HP StorageWorks SAN Virtualization Services Platform Best Practices Guide (5697-0935, May 2011)

TIP: Because ISLs between both sides of the domain may become overloaded, it is important
that they be monitored. It is also important that hosts and their storage are at the same site and
virtual disks are assigned as active on the local DPM. If performance is important during component
failure scenarios, these configurations should be tested.
The only links that are supported for long distance are the ISLs and the only mechanism that is
supported for these links is Fibre Channel (either multimode or single mode). A limit of 100 KM
due to the latency is allowed (one way is 0.5 ms). See the HP StorageWorks SAN Design Guide
for more specific information and a list of approved SFPs for the particular Fibre Channel switches
with ISLs.
The ForceActive utility provides a means to recover automatically from certain kinds of stretched
domain failures. To install the utility, select Browse to "ForceActive" Utililty on the SVSP media
startup screen.
EVA online upgrade and synchronous mirrors
Even if the EVA controller software version supports an online upgrade, the EVA will go offline
after the upgrade for a very short period tolerated by applications. However in the case of a
synchronous mirror, if a single I/O cannot be completed to both source and destination while the
virtual disk is configured to be always synchronized, the virtual disk will fail. The purpose of the
Always Synchronized mode is to ensure the virtual disks are always synchronized. HP recommends
that the synchronous mirror be placed in the Continue on Fail mode temporarily when performing
EVA upgrades, and that dirty regions be enabled to avoid a full copy during the brief outage.
Only upgrade one EVA at a time, using the following procedure:
1. Reduce I/O to the array by quiescing applications, if possible, or reduce the amount of I/O
using the recommendations in the HP StorageWorks Enterprise Virtual Array Updating Product
Software Guide, located at:
http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/c02248322/
c02248322.pdf
2. Check the mode of each SVSP synchronous mirror. If the mode is set to Always Synchronized,
change it to Continue on Fail for the duration of the software upgrade.
3. Continue the software upgrade on each array. When completed, manually initiate a
resynchronization of any synchronous mirror that transitioned to a Journal state.
4. When the synchronous mirrors have completed their Snapsync, and returned to a Normal
state, manually change their mode to Always Synchronized, if this was their mode prior to
the upgrade. Wait for all synchronous mirrors to return to a Normal state before upgrading
another array.
Oracle
SVSP synchronous mirroring within a domain, including a stretched domain, is supported with
Oracle, including RAC clusters. This is currently documented in the Oracle Application Notes
located on the HP Single Point of Connectivity Knowledge (SPOCK) website at http://www.hp.com/
storage/spock. Site registration is required.
48 Synchronous mirroring