Changing Virtual Disk Settings

Some virtual disk settings can be changed in the Settings tab of the Virtual Disk Details page.

In this topic:

Also see:

Storage Profiles to change storage profile settings

Mirror Recovery for information about the auto-recovery setting

Sequential Storage to enable/disable the feature

Continuous Data Protection Operations for CDP settings

Snapshot Operations for setting a preferred snapshot pool

System Health Thresholds to customize the allocated space and I/O latency threshold settings

Resizing a Virtual Disk or Reserved Space

The size of a virtual disk, as well as the amount of reserved pool space for a virtual disk can be changed in the Virtual Disk Details page by clicking Edit at the top of the form and then changing the size. Click Done to save.

Before resizing, read these carefully:

  • Resizing a virtual disk may result in a brief temporary loss of access to hosts.
  • Increasing or decreasing the size of a virtual disk will change the geometry of the LUN seen by the host. Steps may be required on the host in order to recognize the new virtual disk size, such as disk rescanning on the host. Before changing the size of a virtual disk, consult the host operating system documentation to take any necessary actions on the host before and after resizing.
  • Increasing or decreasing the size of a virtual disk while it is served is allowed by the software. Before resizing, consult the host operating system documentation to ensure that the virtual disk can be safely resized while served. The host may require that I/O be stopped and the virtual disk may need to be unserved.
  • When the size of a virtual disk is decreased, the virtual disk will be truncated to the smaller size. Use caution and ensure the disk does not contain data that needs to be preserved before decreasing the size. Any data that resides outside of the smaller boundary will not be moved and will be permanently inaccessible to the host. That data will remain allocated in the pool and cannot be reclaimed unless the data outside of the smaller boundary is zeroed-out before the size is decreased. Before reducing the virtual disk size, ensure that the file system (partition) is reduced to the same size as the new virtual disk size. Then zero-out the data that resides outside of the smaller boundary. After this is complete, then reduce the size of the virtual disk. See Reclaiming Unused Virtual Disk Space in Disk Pools for more information.
  • Virtual disks pending mirror recovery or in recovery cannot be resized.
  • Rollbacks and snapshots cannot be resized unless they are split first. Refer to Continuous Data Protection Operations or Snapshot Operations for more information.
  • Virtual disks used in replication cannot be resized unless split first. Refer to Replication Operations for more information.
  • Virtual disks created from pass-through disks cannot be resized.

Changing the Cache Write-though Mode

Write caching causes write operations to be recorded in the cache first and an acknowledgment is immediately sent back to the operating system confirming the operation before the write operation is written to physical disk. Write caching is enabled by default for single and mirrored virtual disks.

Write caching can be disabled for single or mirrored virtual disks, in which case the virtual disk is put in "write-though" mode. In write-through mode, all write operations to the virtual disk are written directly to the back-end storage and then acknowledged. See Virtual Disks for more information before changing this setting.

Write caching is not supported for dual virtual disks.

To enable or disable write-through mode:

  1. In the Virtual Disk Details page>Settings tab, select or clear the Enable write-through check box as appropriate.
  2. Click Apply.

SCSI Standard Inquiry Data

This information is returned to the host when discovering devices through SCSI inquiries. Certain hosts will require a setting that may be different than the default provided. Under most circumstances these values should not be changed. Changes should not be made when virtual disks are in replication or served to hosts. The default is DataCore (vendor) Virtual Disk (product ID) DCS (revision), [SCSI Device ID]).

Do not change these values unless you are certain that they need to be changed in order for the host to discover the virtual disks or to ensure properly function while using virtual disks. Changing these values unnecessarily or incorrectly will cause errors.

SCSI Device IDs

The SCSI Device ID is intended to be globally unique and is used to identify a particular virtual disk. The SCSI Device ID is prefixed with "naa", followed by a 32-digit hexadecimal number. when changing the ID, the prefix and the first eight digits must be naa.60030D90 to identify a virtual disk. The following 24 digits to complete the number can be any valid hexadecimal number that is unique to the local server group and any server groups of which the virtual disk may interact, for instance in replications. Valid characters are 0 through 9 and a through f.

Use caution when a virtual disk is using duplicate disk IDs and is involved in replications, snapshots, or CDP. If the replication, snapshot or rollback is split, both virtual disks will have the same SCSI device ID. Under these circumstances, the SCSI device IDs on one virtual disk may need to be changed in order to make it unique.

To change the SCSI Standard Inquiry data:

  1. In the Virtual Disk Details page>Settings tab, click Advanced Options.
  2. In the SCSI Standard Inquiry Data area, make the required changes.
  3. Click Apply and reply to the confirmation message to continue.