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Requirements and planning

There are many factors to keep in mind in regards to Universal Volume Manager, including planning for the system and infrastructure, requirements for your system, and application performance. Proper planning and preparation can help you to avoid problems in the future.

Planning workflow

Before you map external volumes to the local storage system, review the information about the planning workflow to ensure that you understand the Universal Volume Manager requirements and implementation procedures.

Use the general order in the following to prepare for Universal Volume Manager:

Procedure

  1. Review System requirements .

  2. Verify that the external storage system whose volumes you want to map is supported by Universal Volume Manager. See Appendix A, Supported external storage systems.

  3. Verify that the functionality you want is supported for mapped external volumes. See Supported software for external volumes.

  4. In the external storage system, select a port and set parameters, as necessary.

  5. In the local storage system, identify the port to be connected to the external storage system and make sure it is specified as an external port.

  6. Plan data paths from the local storage system to the external storage system. See External paths, path modes, and configurations .

  7. In the external storage system, prepare volumes for use in the local storage system. For example, if you plan to use an external volume for replication, verify that it meets the requirements for replication software.

    For instructions and additional information, see External volume requirements .

  8. In the local storage system, configure the external volume groups to which you will assign the external volumes during the mapping operation. See External volume groups .

  9. Optionally, change the default values of the mapping settings before performing the operation. See External volume policy settings and functions.

System requirements

You can perform Universal Volume Manager (UVM) operations between the local storage system and volumes in an external storage system.

The following table lists the general requirements for all UVM components.

Item

Description

External storage systems

For details about the supported external storage systems, see Supported external storage systems.

UVM software license

Required. For installation and operations instructions, see the System Administrator Guide.

RAID level

The RAID level for all external volumes is RAID 1. RAID 1 is displayed or used in the following cases:

  • Internal processing of the local storage system.
  • Information about the external storage system that is reported to a higher-level device (OS).

Note: The local storage system uses RAID 1 cache management for external volumes. However, the external storage controller manages the physical RAID method. In addition, a hyphen is displayed instead of the RAID level in Device Manager - Storage Navigator windows.

Maximum number of ports in external storage systems that can be mapped

  • Fibre channel: 1,024 for each port
  • iSCSI: 512 for each port (127 or less is recommended)

Maximum number of external volumes that can be mapped

  • 63,232
  • For Thin Image and Dynamic Provisioning, the total number of external and virtual volumes must not exceed 63,232.

Maximum number of external volume groups

VSP G1x00 and VSP F1500:

Maximum number of external volumes registered in each external volume group

VSP G1x00 and VSP F1500:

Number of mapping paths

  • One required.
  • Two or more recommended
  • Maximum = 8 per external volume

Maximum capacity of an internal volume

If mapping an external volume of up to 4TB in an external storage system, the internal volume will be defined as 1 LDEV (LU), which is the same as the external volume.

You cannot access data that exceeds the maximum capacity of the external volume.

Minimum capacity of an external volume

  • If Data Direct Mapping is enabled:

    About 8,192 MB (16,777,216 blocks) per external volume

  • If Data Direct Mapping is disabled:

    About 47 MB (96,000 blocks) per external volume

Maximum capacity of an external volume

  • If mapping an external volume with more than 4 TB by using a virtual volume for which Data Direct Mapping is enabled:

    256 TB (549,755,813,888 blocks) per external volume

    You can create a volume larger than 256 TB, but can only use 256 TB as a mapped external volume. Data in the additional area cannot be accessed.

  • If mapping an external volume with more than 4 TB without using a virtual volume for which Data Direct Mapping is enabled:

    59.99 TB (128,849,011,200 blocks) per external volume

    You can create a volume larger than 59.99 TB, but can only use 59.99 TB as a mapped external volume. Data in the additional area cannot be accessed.

For details about mapping using virtual volumes for which Data Direct Mapping is enabled, see the Provisioning Guide.

Maximum number of external volumes that can be mapped per port

If one external port is connected to several target ports through switches, the maximum number of LUs defined for the connected target ports is 4,096.

Planning considerations for external storage systems

The performance of an external storage system is affected by local system operations. Conversely, performance of the host and local system are affected by the attributes assigned to the external system.

Note the following regarding performance:

  • The performance and status of the external system affects the performance of the mapped external volume. A high number of processes running on the external system slows the processing speed of read/write requests and might cause a missing interrupt handler.
  • If the host connected to the local storage system issues several I/O requests to be processed by the external storage system, the requests from the host might time out.
  • When you run commands from the local storage system that result in more I/O requests being processed than the external storage system can handle, the commands might time out and an error might occur.
  • When there is a process running between an external volume and the host, it is important that the Blocked Path Monitoring time of the external volume is the same as or shorter than the timeout period of the process that is running on the host. If the value of the Blocked Path Monitoring time setting is longer than the timeout period of the process running on the host, the process on the host might time out if the power supply is interrupted or if an error occurs in the external storage system.
  • You can improve the host I/O performance for sequential writes to mapped volumes by setting system option mode (SOM) 872 to ON. For more information, contact customer support.

External volume requirements

External volumes must meet the Universal Volume Manager requirements.

When planning external volumes, note the following:

  • You can use existing data in an external volume after it is mapped to the local storage system, with the following restrictions:

    • To perform host I/O operations, you must set an LU path from the target port to the mapped volume.
    • An external volume cannot be mapped to a DP Pool that has DP-VOLs with the capacity saving function enabled. Capacity saving features are not supported for external storage.
    • You cannot enable the capacity saving function on a DP-VOL from a DP Pool that has pool volumes from external storage.
  • The maximum or minimum available capacity of an external volume depends on the emulation type you specify when mapping the volume.
  • You cannot access data stored in an external volume that exceeds the allowed maximum capacity. See the Maximum capacity of an external volume row in System requirements .
  • Make sure that a mapped external volume is accessed only from the local storage system.

    • Make sure that a mapped external volume is not accessed from a host that is connected to the external storage system.
    • Make sure that a mapped external volume is not manipulated by a copy function or any other functions of the external storage system.
    • Accessing a mapped external volume from the external storage system requires that the volume mapping be disconnected first.
  • External volumes that are reserved by a host cannot be mapped as internal volumes. To map these volumes, cancel the reserve settings, remove host access to the volumes, and then perform the mapping operation.
  • Do not map multi-platform volumes of external storage systems as internal volumes.
  • If an external storage system that uses control unit path ownership is connected to the local storage system, configure the external path to the primary controller in the external storage system as the primary path.

    Ownership is the exclusive right to control volumes. A controller that has ownership is called a primary controller. If the external path is connected to a controller that does not have ownership, and the path is configured as primary path, the ownership will be transferred, which might affect performance.

  • A management LU cannot be used as an external volume.

    A management LU receives commands from an application, because it controls or manages the application, and stores control information from the application. An example of a management LU is a Universal Xport LU. (A CCI command device is not a management LU.)

    Before performing the external volume mapping operation, perform one of the following operations on the external storage system:

    • Delete the management LU from the port to be connected to the local storage system.
    • Make sure that at least one LU is used for data storage and has a smaller LUN (LU number) than the management LU's LUN. Also make sure that the data storage LU is set to the port connected to the local storage system.
    • Use the security function and configure the access attribute of the management LU to prohibit read and write operations.

    An external storage system that has a management LU might not be recognized by the local storage system.

The following requirements apply to only to VSP Gx00 models and VSP Fx00 models:

  • You cannot map an external volume whose capacity is smaller than the minimum capacity required for internal volumes.
  • Before the settings of an external storage system are changed, mapping to volumes on the local storage system must be removed by selecting Disconnect External Volumes. After the external storage system settings are changed, volumes can be remapped. Unless external volumes are remapped, they cannot be used on the local storage system.

  • If an LU path is configured on an internal volume mapped to an external volume, the external volume mapping cannot be deleted.

  • Mapping cannot be deleted for a volume used in a pair for the following programs:

    • TrueCopy
    • Universal Replicator
    • ShadowImage
    • Thin Image
    • Global-active device
  • Mapping cannot be deleted for an external volume configured as a pool volume.

  • Mapping cannot be deleted for an external volume configured as a quorum disk.

Cache use and external storage performance

If you enable Cache Mode, you must define a cache logical partition (CLPR). A CLPR helps to protect performance of the local storage system when the I/O rate exceeds the capabilities of the external storage system.

The Cache Mode setting, which you specify during a mapping operation, and a proper cache configuration affect the performance of the external storage used with the local storage system.

When data is written to a mapped external volume, Cache Mode controls when the write-complete response is sent to the host:

  • If Cache Mode is enabled, the write-complete response is sent when the write data is in the cache of the local storage system.
  • If Cache Mode is disabled, the write-complete response is sent when the write data is accepted by the external storage system.

Disabled is the safest setting and is recommended when there is a possibility that the I/O rate will exceed the short term capabilities of the external storage.

Enabled can adversely impact overall performance of the local storage system if the I/O rate exceeds the performance capabilities of the external system. If you enable Cache Mode, you must use the same formula for sizing cache in both the local and external storage systems.

Cache Mode effects with other Hitachi software

Note the following additional effects regarding the Cache Mode setting:

  • Data that is not written by the host (for example, data written by ShadowImage) is asynchronously destaged to the external storage system regardless of the Cache Mode setting.
  • When you enable the cache mode, consider the system load. Normally when you enable the cache mode, write response or host write performance improves because data written by the host is applied to the external storage system asynchronously by using the local storage system's cache.

    However, if the system load is high (for example, cache usage rate exceeds 60%), the local storage system suppresses write operations from the host in order to lower the load. Because of this, even if the cache mode is enabled, write responses from the host might become slower or host write performance might become lower than when the cache mode is disabled.

  • : The external volumes in a Dynamic Provisioning pool must all use the same Cache Mode setting, either Enabled or Disabled.
  • : Dynamic Tiering pool volumes require Cache Mode to be set to Enabled.

External volume groups

During the mapping operation, you assign the external volume to an external volume group (ExG). This allows you to organize external volumes used for similar purposes to a particular group or groups.

For example, you might want to assign mapped volumes in the same external system to a specific ExG. Or, you might assign volumes used in a particular function, such as ShadowImage or Universal Replicator, to an ExG, even if the data is stored in different external storage systems.

You could also use ExGs to correspond to the external system's physical disk grouping, such as a RAID group.

You assign external volume group numbers during the mapping procedure.

External paths, path modes, and configurations

The external path is the physical link from the local storage system port to the external storage system port. You prepare the ports on the local and external systems and then set up the external path prior to mapping your external volumes.

External paths

A path consists of cables and possibly switches. You configure your path according to bandwidth considerations, which include distance, speed, and performance requirements.

Because workload can spike and cable or switch failures can occur, we strongly recommend that you set up redundant external paths. A maximum of eight paths can be used per mapped external volume. Multiple paths (that is, redundancy) allows you to perform I/O operations with external volumes regardless of workload or path failure.

With multiple paths, the external storage system determines how they are used: some systems use one primary path with alternates available as backups (Single path mode); other systems allow all paths to be used at the same time, distributing I/O among them (Multi path mode). The path storage system's mode cannot be changed. With both modes, you place the paths in path groups and prioritize each path.

Single path mode

For Single path mode, the external path with the highest priority (primary path) is used for I/O to the external volume. If the primary path cannot be used, the path with the second highest priority is used.

The following figure illustrates how failure is handled with redundant paths in Single path mode.

GUID-D825D905-38AC-4495-B17A-7A41E244AC50-low.png

When you restore a path with higher priority than the currently-used path, I/O is switched to the restored path.

Multi path mode

For Multi path mode, all paths are used for I/O to the external volume. This distributes workload in a round-robin process.

The following figure illustrates how failure is handled with redundant paths in Multi mode.

GUID-81A4EE23-3A36-4E19-A21E-771F71955355-low.png
NoteWhen you restore a path, use of the restored path is resumed.

Supported external system path mode for external volumes

Single or Multi path mode displays in Device Manager - Storage Navigator for external volumes on the External Path Group window. Path modes are based on the external storage system and cannot be changed.

In ALUA mode, the storage system uses all paths that are defined. The storage system performs I/O operations for external volumes through load balancing with the use of several paths (round-robin control). The storage system does not use external paths connected to ports that are in Passive status.

Load Balance Mode

When the path mode of an external volume is Multi or ALUA, you can select an I/O mode for the external storage system.

  • Depends on the selected external volume(s): If Enable is set for ALUA Settable on the external volume, Normal Round-robin is set for Load Balance Mode automatically. If Disable is set for ALUA Settable, Disable is set for Load Balance Mode automatically.
  • Normal Round-robin: Normal multi-path I/O control system. This distributes I/O to several paths on which I/O operation is enabled for the external storage system. Specify this if Extended Round-robin might lower I/O performance. This mode is recommended when the number of sequential I/O operations is small.
  • Extended Round-robin: Extended multi-path I/O control system. I/O is distributed to several paths on which I/O operation is enabled for the external storage system. For sequential I/O, the external volume is divided into sections at regular intervals. In this case, the same path is used for I/O within the same section which reduces the frequency of I/O distribution. You can improve the read speed by using the cache function of the external storage system for sequential I/O operations. This mode is recommended when the number of sequential I/O operations is large.
  • Disable: I/O operation is performed with only one path that is normal and has the highest priority. The same operation applies as that for Single path mode. When Disable is set for Load Balance Mode, load distribution is not performed. This mode is not recommended.
CautionDepending on the external storage type and system configuration, performance might not be improved when Extended Round-robin is set. In that case, Normal Round-robin is recommended.

The following table shows the path mode for many of the supported external storage systems. The table also shows the abbreviation used in Device Manager - Storage Navigator. If your system is not shown below, refer to https://knowledge.hitachivantara.com/Documents.

Storage System Reference
Hitachi Virtual Storage Platform G200, G400, G600, G800, Hitachi Virtual Storage Platform F400, F600, F800
  • Path Mode: Multi
  • Displays as VSP Gx00
Hitachi Virtual Storage Platform G350, G370, G700, G900, Hitachi Virtual Storage Platform F350, F370, F700, F900
  • Path Mode: Multi
  • Displays as VSP Gx00
Hitachi Virtual Storage Platform G1000, G1500, F1500
  • Path Mode: Multi
  • Displays as VSP G1000
Unified Storage VM
  • Path Mode: Multi
  • Displays as HUS VM
Hitachi Virtual Storage Platform
  • Path Mode: Multi
  • Displays as VSP
Hitachi Universal Storage Platform V
  • Path Mode: Multi
  • Displays as USP V
Hitachi Universal Storage Platform VM
  • Path Mode: Multi
  • Displays as USP VM
Hitachi TagmaStore® Universal Storage Platform
  • Path Mode: Multi
  • Displays as USP
Hitachi TagmaStore® Universal Storage Platform
  • Path Mode: Multi
  • Displays as NSC
Hitachi Unified Storage
  • Path Mode: Multi
  • Displays as HUS
Hitachi Adaptable Modular Storage
  • Path Mode:

    - Multi: AMS2500, AMS2300, AMS2100, or AMS2010

    - Single: AMS1000, AMS500, or AMS200

  • Displays as AMS
Hitachi Workgroup Modular Storage
  • Path Mode: Single
  • Displays as WMS
Hitachi Simple Modular Storage
  • Path Mode: Multi
  • Displays as SMS
Hitachi Lightning 9900 V Series
  • Path Mode: Multi
  • Displays as 9970V and 9980V
Hitachi Lightning 9900 Series
  • Path Mode: Multi
  • Displays as:

    - Lightning 9960: 0400

    - Lightning 9910: 0401

Hitachi Thunder 9500V series
  • Path Mode: Single
  • Displays as 9500V
Hitachi SANRISE Universal Storage Platform
  • Path Mode: Multi
  • Displays as USP
Hitachi SANRISE Network Storage Controller
  • Path Mode: Multi
  • Displays as NSC
Hitachi SANRISE 9900V series
  • Path Mode: Multi
  • Displays as 9970V and 9980V
Hitachi SANRISE 9500V series
  • Path Mode: Single
  • Displays as 9500V
Hitachi SANRISE 2000 series
  • Path Mode: Multi
  • Displays as:

    - SANRISE 2800: 0400

    - SANRISE 2200: 0401

HP Virtual Storage Platform VX7
  • Path Mode: Multi
  • Displays as XP7
HP Virtual Storage Platform VP9500
  • Path Mode: Multi
  • Displays as P9500
A/H-6593
  • Path Mode: Multi
  • Displays as 300
HP H24000
  • Path Mode: Multi
  • Displays as 24000
HP H20000
  • Path Mode: Multi
  • Displays as 20000
HP SANRISE H12000
  • Path Mode: Multi
  • Displays as 12000
HP SANRISE H10000
  • Path Mode: Multi
  • Displays as 10000
HP SANRISE H1024/ H128
  • Path Mode: Multi
  • Displays as 1024 and 128
HP SANRISE H512/H48
  • Path Mode: Multi
  • Displays as 512 and 48
HP SANRISE H256
  • Path Mode: Multi
  • Displays as 256
HP XP7
  • Path Mode: Multi
  • Displays as XP7
HP StorageWorks P9500
  • Path Mode: Multi
  • Displays as P9500
HP XP24000
  • Path Mode: Multi
  • Displays as 24000
HP XP20000
  • Path Mode: Multi
  • Displays as 20000
HP XP12000
  • Path Mode: Multi
  • Displays as 12000
HP XP10000
  • Path Mode: Multi
  • Displays as 10000
HP XP1024/XP128
  • Path Mode: Multi
  • Displays as 1024 and 128
HP XP512/XP48
  • Path Mode: Multi
  • Displays as 512 and 48
HP XP256
  • Path Mode: Multi
  • Displays as 256
HP StorageWorks Enterprise Virtual Array 3000/4000/5000/600 0/8000
  • Path Mode: Single
  • Displays as EVA
SVS200
  • Path Mode: Multi
  • Displays as SVS200

External path configurations - direct and switch

Recommendations for setting up direct and switch external path configurations.

Direct connection

The following figure shows redundant paths in a direct connection configuration. External storage system ports, External port A and External port B, are connected to the local system ports, CL1-A and CL2-A (which are specified as external ports). For greater redundancy, Path 2, the alternate path, uses ports of a different cluster in both the local and external storage systems.

GUID-88A2FC6F-587E-4BBB-ADA2-3E77EB389CBB-low.png
Switch connection

The following figure shows redundant paths with switches. Ports in the local system are connected to ports in the external system through the switch. The paths use ports of different clusters for increased redundancy.

GUID-B657186D-6261-420F-9864-F44FB15688E3-low.png

The following figure shows an invalid configuration. Two paths are set between the internal and external volumes, but only one port is specified for the local storage system. The port is connected to ports in the external storage system through the switch. Because ports of two different clusters must be set in the local storage system, the following configuration is not recommended.

GUID-1179587E-C484-4472-8A43-AD423C8BDAC4-low.png

Mapping policy

The mapping policy is a list of settings that are required for mapping external volumes. Setting mapping policies before you perform a mapping operation is the easiest way to configure your mapping settings. Policies are already available and the user can change the default value. See External volume policy settings and functions to review the settings and edit them if desired.

Considerations for external volume attributes

  • All the external volume attributes of an LDEV created within the external volume are the same. These attributes persist even when an LDEV is recreated with the VLL function.
  • All LDEVs within an external volume have the same cache mode.
  • Attributes, such as port or LUN security, set for a volume on the external storage system side persist when the volume is mapped.
  • Mapped volume settings can be made on the local storage system side as necessary.
  • Volumes for which the T10 P1 attribute is enabled cannot be specified as an external volume.

Considerations for using iSCSI

Before configuring a system that uses iSCSI, review the following considerations. For details about iSCSI, see the Provisioning Guide. For other considerations when using Universal Volume Manager, see Planning considerations for external storage systems.

Considerations for external paths
  • When adding an external path to a path group, make sure that it uses the same protocol as the other paths in the group. External paths for Fibre Channel and iSCSI cannot exist in the same path group.
  • If iSCSI is used for an external path, set Blocked Path Monitoring to at least 40 seconds (default). If you set a lower value, the external path might be blocked due to network delays, including the spanning tree functionality of a switch.

    In addition, if external volumes are accessed from a host, set the command timeout period of the host to a value greater than the value of Blocked Path Monitoring. Otherwise, commands from the host might time out when the external storage system is turned off or a failure occurs.

  • After adding an iSCSI path, execute the login test for the iSCSI target to check if you can log in. If there is an iSCSI path from which you cannot log in to the iSCSI target, attempts to connect to the path are made, and the load to storage systems or networks may become high. If this happens, external volumes might not be recognized.
  • For an iSCSI path from which you cannot log in to the target, edit the iSCSI target or check settings of the external storage system to make sure you can log in. Alternatively, remove the iSCSI path.
Considerations for data paths
  • When replacing Fibre Channel or iSCSI data paths, first remove any external paths that use the data paths to be replaced.

  • Use the same protocol for data paths between a host and a storage system, or between storage systems.

  • When Fibre Channel is used in a data path between a host and a storage system, and iSCSI is used for a data path between storage systems, different protocols are used in the data path. In this case, set a value which is equal to or greater than the timeout period for the command between storage systems as the timeout period of the command between the host and the storage system.

Considerations for ports
  • When you change parameter settings for an iSCSI port, the iSCSI connection is temporarily disconnected, and then reconnected. Therefore, you should change parameter settings when the I/O load is low to reduce impact on the system.

  • When you change settings for an iSCSI port connected to a host, log information might be output to the host. However, this does not indicate a failure. In a system that monitors system logs, if an alert is issued, change the iSCSI port settings, and then check if the host is reconnected.

  • For the iSCSI port connecting to storage systems or to the host, set Delayed ACK to Disable.

    If Delayed ACK is set to the default value Enable, the host might take a long time to recognize external volumes. For example, 2,048 volumes might take 8 minutes.

  • In the Edit Ports window, Selective ACK is set to Enable by default. Do not change this setting.

  • In an environment in which a delay occurs in a line between storage systems, such as long-distance connections, we recommend trying various sizes, and then setting an optimal window size of iSCSI ports in storage systems at the primary and secondary sites. The maximum value you can set is 1,024 KB. Note that the default window size is 64 KB.

  • In Universal Volume Manager, an external path connection is established for each iSCSI target of an external storage system. The maximum number of iSCSI external paths for each port is 512. However, we recommend you set no more than 127 external paths for each port.

  • iSCSI ports do not support the fragmentation (splitting packets) functionality. If the maximum transfer unit (MTU) of a switch is smaller than the MTU of the iSCSI port, packets are lost and communication might not be performed correctly. To avoid this problem, set the switch MTU to a value equal to or greater than the iSCSI port MTU. Note that the iSCSI port MTU must be at least 1500.

    In a WAN environment in which the MTU value is smaller than 1500, fragmented data cannot be sent or received. In such environment, set a smaller value for the maximum segment size (MSS) of the WAN router according to the WAN environment, and then connect the iSCSI port. Alternatively, use iSCSI in an environment in which the MTU value is 1500 or higher. For details about MTU values for the switch and how to set them, see the documentation for the switch.

  • To use Universal Volume Manager on iSCSI ports for which the virtual port mode is enabled, you must use CCI. Additionally, you must use CCI to enable the virtual port mode. Do not set external paths from multiple virtual ports associated with a single iSCSI port of the local storage system to the same iSCSI port of an external storage system. We recommend that you use different iSCSI ports for paths to external storage systems and their alternate paths.

  • A single port can be used for connections to hosts (target attribute) and storage systems (initiator attribute). However, to minimize the influence to the system if a failure occurs either in a host or storage system, we recommend that you connect ports for hosts and storage systems to separate CHBs.

Notes on network settings
  • We recommend that you disable the spanning tree setting on the port of a switch connecting to an iSCSI port. If you enable the spanning tree functionality of a switch, packets might not be looped in the network when the link is up or down. If this happens, the packets might be blocked for approximately 30 seconds. If you must enable the spanning tree settings, enable the port fast functionality of the switch.

  • In a network path between storage systems, if you use a line whose transfer speed is slower than the iSCSI port, packets are lost and the line quality is degraded. To avoid this problem, configure the system so that the transfer speed for iSCSI ports and lines is the same.

  • The delay in the line between storage systems varies depending on the system environment. Therefore, validate the system first, and then check the optimum window size settings of iSCSI ports. If the influence of the line delay is unacceptable, consider using devices for optimizing or accelerating the WAN speed.

  • If you use iSCSI, packets are sent or received using TCP/IP. Therefore, the number of packets might exceed the capacity of the communication line, or packets might be resent. As a result, performance might be greatly affected. Therefore, in critical systems that rely on performance, use Fibre Channel.

  • If the external storage system is in the HUS 100 series, the number of iSCSI targets you can search for is limited. If the iSCSI target name is 47 characters (default), you can search up to 170 iSCSI targets.

Considerations for using Fibre Channels

When configuring a system using Fibre Channels, you need to consider the following restrictions. For details about Fibre Channels, see the Provisioning Guide.

  • When you use Fibre Channel as an external path, if you specify Auto for Port Speed, specify 10 seconds or more for Blocked Path Monitoring. If you want to specify 9 seconds or less, do not set Auto for Port Speed.
  • If the time specified for Blocked Path Monitoring is not long enough, the network speed might be slowed down or the period for speed negotiation might be exceeded. As a result, paths might be blocked.

Copying external storage system data

You can use copy pairs to copy data from an external storage system to the local storage system. External volumes can be set up as either a P-VOL or S-VOL.

Using an external volume as a P-VOL to copy data

GUID-C82884E9-5B0E-4C04-89DB-ACECE67DF69F-low.gif
  1. Use Universal Volume Manager to map the external volume (A) to an internal volume (B) of the local storage system. You will use volume (B) as the P-VOL of a copy pair.

  2. Check the capacity of internal volume (B) to which external volume (A) is mapped, and select a copy destination volume (C) that has the same or greater capacity than volume (B). You will use copy destination volume (C) as the S-VOL of the copy pair.

  3. If the copy destination volume (C) is bigger than volume (B), use the VLL function to create a CV that has the same capacity as volume (B). Create the CV using the block value displayed in the Mapped Volumes tab in the selected external path group window.

  4. Create the copy pair using volume (B) as the P-VOL and volume (C) as the S-VOL. This configuration makes a copy of external volume (A).

Using an external volume as an S-VOL to copy data

GUID-8FC2B08D-9939-4CBB-9B84-19C5E5EFAD9F-low.gif
  • Use Universal Volume Manager to map the external volume (A) to an internal volume (B) of the local storage system. You will use volume (B) as the S-VOL of a copy pair.

  • Check the capacity of internal volume (B) to which external volume (A) is mapped. If the capacity of internal volume (B) is different than the copy source volume (C), use the VLL function to create a CV that has the same capacity as the copy source volume (C).

  • Create the copy pair using copy source volume (C) as the P-VOL and volume (B) as the S-VOL. This configuration makes a copy of the source volume on external volume (A).