HP StorageWorks SAN Virtualization Services Platform 3.0.2 Release Notes (5697-0347, May 2010)

Period of high back-end load after a DPM reboot when synchronous mirror virtual disks are
used
In a configuration with synchronous mirror virtual disks, there may be a period of higher than normal
load on the back-end storage arrays after a DPM reboot. This will vary depending on the capacity
of the synchronous mirror virtual disks and with the load and write patterns on those virtual disks
before the DPM reboot. To reduce performance impact on production activity, HP recommends that
DPM reboots (for example, during a DPM upgrade) be scheduled for off-hours or during a maintenance
window.
I/O errors/timeouts when performing failover on large numbers of synchronous mirror virtual
disks
If there is a heavy load of I/O on a large number of synchronous mirror virtual disks and an event
occurs that requires a large number of virtual disks to be failed over at the same time (for example,
a reboot of a DPM), it is possible that I/O errors or timeouts may be returned to the hosts. HP
recommends that operations requiring a DPM reboot (for example, a DPM firmware upgrade),
particularly in a large environment, be scheduled for off-hours or during a maintenance window, or
manually fail over each synchronous mirror group, one at a time.
DPM reboots when a host has two different host types or personalities on two different SVSP
domains
If a DPM is connected to two different SVSP domains, and a host is configured for a different host
type or personality on each of the VSM domains, the DPM may enter a continual reboot mode. A
host with two different host types or personalities is an incorrect configuration and is not supported.
DPM ports connected to a 4 Gb Fibre Channel switch may sometimes auto-negotiate to 2 Gb
speed
In some cases, the DPM ports may negotiate to a slower speed than their capability. In these cases,
verify the SFPs in the DPM and switch are supported and that there is not an unusually high number
of errors reported for that link in the port statistics. If there are errors, replace the SFPs and cable. The
port can also be manually set to 4 Gb speed on the DPM.
DPM NTP configuration does not work with Windows domain controllers
The DPM only supports NTP servers that support network time protocol query (ntpq) and the full
RFC-1305 specification. In particular, Windows only implements ‘Simple NTP’ and is not supported
by the DPM as an NTP server.
DPM reboot when unpresenting/re-presenting back-end virtual disks
Under certain circumstances, if permissions to a back-end virtual disk are removed from the SVSP
system (DPM and VSM), and then permissions are restored, or a new back-end virtual disk is created
with the same LUN number, the DPM may unexpectedly reboot. HP recommends that such operations
be scheduled for off-hours or during a maintenance window.
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