HP StorageWorks Snapshot XP user guide (T1713-96023, October 2006)

Although you estimate copied data capacity and set pool capacity according to the information in this
section, if pool capacity exceeds the threshold, implement the measures described in Troubleshooting
Snapshot XP.
Using externa
l LUs as pool-VOLs
By using E xter
nal Storage XP, you can connect multiple arrays to the XP12000/XP10000/SVS200 array.
In that case, t
he original XP12000/XP10000/SVS200 array is called the local array, and the connected
storage arrays are called external arrays. A volume in an external array is called an external LU.A
volume in the local array is called an internal storage virtualizer LDEV (referred to as an internal LD EV).
If External Storage XP is installed, you can use internal LDEVs and external LUs as pool-VOLs. However,
external LUs are more likely to fail than internal LDEVs. In addition, solutions for external LU failures are
more complicated than those for internal LDEV failures. To minimize the effects of failures, H P recommends
using exter
nal LUs as follows:
• Specify external LUs of only one external array for one pool
• Do not specify both internal LDEVs and external LUs as pool-VOLs in one pool
You can spe
cify the external LUs of several external arrays for one po ol, or use both internal LDEVs and
external LUs as pool-VOLs in one pool, but in that case, remember that problems such as volume blockade
can occur more e asily. For examp le, if a problem occurs and the external LUs being used as a pool-VOL
are blocked, the pool becomes blocked as well. For more information, see Recovering blocked pools.
For more information about external arrays and solutions for errors related to external LUs, see the
HP Storag
eWorks External Storage XP user guide.
Notes on using Snapshot XP
This section describes switching off the power supply and replacing the microprogram offline while
Snapshot XP is in use.
Switching off the power supply
Before switching off the power supply while Snapshot XP is running, stop host I/O operations. When
switching on the power supply, Snapshot XP behaves differently depending on whether information in
shared memory remains before and after switching off the power supply.
• If info
rmation in shared memory remains before and after switching off the power supply
You can
usually use the pools and Snapshot XP pairs you used before switching off the power.
Howev
er, since the a rray checks the status of pools and po ol volumes, if pool volumes are blocked
at that time, the pool is blocked and the status of Snapshot XP pairs changes to PSUE. When this
occurs, you must recover the pools after switching on the power. For more information, see Recovering
blocked pools.
• If in
form ation in shared memor y is lost af ter switching off the power supply
The a
rray has a battery to maintain information in shared memor y. However, when a certain time
perio d elapses after the breaker is turned off, the battery dies a n d information in shared memory
is lost. If information in shared m em o ry is lost after switching off the power supply, information
about pools and Snapshot XP pairs is erased. Therefore, you must create pools and pairs again
after switching on the power.
For more information about the amount of time before information in shared memory is lost when the
bre
aker is turned off, contact your HP acc ount suppor t representative.
Re placing the microprogram offline
Replacing the microprogram is usually performed online, but in some cases, such as when the shared
memory configuration must be changed, re placing the microprogram is performed offline. If you replace
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Using Snapshot XP