HP 3PAR VMware ESX Implementation Guide

NOTE: To avoid possible issues described in VMware KB 2007427 and KB 2014849, automatic
VAAI Thin Provisioning Block Space Reclamation (UNMAP) should be disabled on ESXi 5.0 GA.
The KB articles are available on the VMware Knowledge Base website: VMware
ESXi 5.0 Update 1 and later includes an updated version of vmkfstools that provides an option
[-y] for sending the UNMAP command regardless of the ESXi host’s global setting. You can use
the [-y] option as follows:
# cd /vmfs/volumes/<volune-name>
vmkfstools -y <percentage of deleted block to reclaim>
NOTE: The vmkfstools -y option does not work in ESXi 5.0 GA.
ESXi 5.5 introduces a new command in the esxcli namespace that allows deleted blocks to
be reclaimed on thin provisioned LUNs that support the VAAI UNMAP primitive.
# esxcli storage vmfs unmap -l <datastore name>
The vmkfstools -y command is deprecated in ESXi 5.5. See VMware KB 2057513 for more
information.
UNMAP also frees up space if files are deleted on UNMAP-supported VMs such as Red Hat
Enterprise 6, as long as it is a RDM LUN on a TPVV storage volume—for example, for RDM volumes
on a Red Hat VM using the ext4 filesystem and mounted using the discard option.
# mount —t ext4 —o discard /dev/sda2 /mnt
This causes Red Hat 6 VM to run the UNMAP command and release space back on the array for
any deletes in that ext4 file system.
Out-of-Space Condition for ESX 4.1 and ESXi 5.x
The out-of-space condition, aka "VM STUN", is implemented in ESX 4.1 and ESXi 5.x and is
supported as of HP 3PAR OS 2.3.1 MU2. This OS feature does not depend on the VAAI plug-in
and applies to TPVV volume types.
When the TPVV volume cannot allocate additional storage space or cannot grow because the
storage system is out of disk space, it sends a Check condition with "DATA PROTECT" sense key
error and additional sense "SPACE ALLOCATION FAILED WRITE PROTECT". As a result, ESX
pauses the VM and displays an 'Out of Space' message to the user in the Summary tab of the VM
on vSphere, with the options of Retry or Cancel. In the pause-VM condition, read requests and
rewrites to the allocated LUN blocks are allowed, but writing to a new space is not allowed. Ping,
telnet and ssh requests to the VM are not honored. The storage administrator must add additional
disk space or use storage vMotion to migrate other unaffected VMs from the LUN. After additional
disk space is added, use the Retry option on the warning message to bring the VM back to the
read-write state. If you select the Cancel option, the VM reboots.
In the following example, an HP 3PAR StoreServ Storage TPVV volume was created with a warning
limit of 60%, as shown in the showvv -alert command.
52 Configuring the Host for a Fibre Channel Connection