3PAR InForm Operating System 2.3.1 Release Notes (320-200178 Rev D, May 2010)

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3PAR InForm Operating System Release Notes InForm OS Version 2.3.1
2.7 Limitations of the InForm OS
2.7.1 Fibre Channel/SCSI Interface
The InForm OS does not provide user-level control on write caching via the SCSI mode select
command. Write-caching is on by default. Deferred errors will never be reported after status is
sent for a write command. The InServ Storage Server system software may go into write-
through mode while handling certain events such as loss of battery charge or a faulty node.
The following SCSI commands are supported but are effectively null operations:
rezero_unit, format_unit, seek, verify, sync_cache, send_diag. The SCSI command
write verify performs a write operation but not a verify operation.
Head-of-queue and ordered-queue are not supported. Simple-queue currently defaults to
unrestricted reordering.
2.7.2 Deleting Large Snapshot Volumes
For volumes that are extremely large and/or have a large amount of ongoing writes, deleting
snapshots of the volume may take a long time. This is particularly the case for volumes larger
than 100GB. Times in excess of 20 minutes have been observed in the worst cases. As of release
2.1.2, this no longer blocks growth of TPVVs, CPVVs, and CPGs, which previously could cause
host writes to fail. However, this will still make both the GUI and CLI unresponsive for the
duration of the snapshot deletion.
In addition to manual deletion via the
removevv command, snapshot deletions may be
performed automatically by the use of Physical Copy or Remote Copy. Remote Copy makes
particularly heavy use of snapshot deletion when it is configured to use asynchronous periodic
mode.