IBM DS3950, Инструкция по установке, использованию и обслуживанию, Страница: 162 / 252

Consider backing up your data if you use this method. This safeguards your
data if the restoration and reconfiguration process fails or the new drive
malfunctions.
The method you use depends on the following considerations:
v
Which method most closely matches the drive upgrade procedure in the
operating-system or the storage-management software documentation.
v Which RAID level is used on the affected drives. (RAID 0 requires you to
replace all the E-DDMs at the same time.)
v
How much downtime is acceptable as you swap the E-DDMs.
v
The number of E-DDMs in an array. Replacing E-DDMs one at a time is better
suited for arrays consisting of 3 to 5 E-DDMs. If you have more than 10
E-DDMs or arrays that are comprised of high capacity SATA E-DDMs, consider
replacing all E-DDMs at the same time.
v
How much risk of losing data is acceptable. Because the array will be in a
degraded state during the RAID array reconstruction and copyback process as
result of replacing a drive in the array, any new E-DDM failure will cause the
array to fail (causing a loss of data availability and even a loss of data). The
duration of the reconstruction and copyback process can be quite long,
depending on the size of the RAID array.
v
How extensive will the data be changed while the array is in a degraded state
during the RAID array reconstruction and copyback process as result of
replacing an E-DDM in the array. The more extensive the data changes, the more
work that will need to be performed to restore the data in the event that the
array failed because of an addition E-DDM failed while the array is in degraded
state.
Replacing all E-DDMs at the same time
Use this procedure to replace all E-DDMs at the same time. You must use this
method if you are upgrading E-DDMs containing RAID 0 logical drives. All the
data currently on the E-DDMs is lost when you replace the E-DDMs; therefore, you
must back up all data that is currently on the E-DDMs. This procedure also
requires you to turn off the storage expansion enclosures and the DS3950, which
makes the storage subsystem (and any attached storage expansion enclosures)
inaccessible to other users.
Attention: After you remove an E-DDM CRU, wait 70 seconds before replacing
or reseating the E-DDM CRU to allow it to properly spin down. Failure to do so
might cause undesired events.
To replace all the E-DDMs at the same time, perform the following steps:
1. Read the following information:
v
The information in “Replacing multiple E-DDMs” on page 133, particularly
the paragraphs that discuss the differences between the two possible
upgrade procedures
v
The information in your software documentation regarding E-DDM
upgrades and installation
v
The documentation that comes with the new E-DDMs
Read all precautionary notes, kit instructions, and other information. Kit
instructions often contain the most current information regarding the
E-DDMs and their installation, plus upgrade or servicing procedures.
Compare the kit instructions with this procedure to determine if you need
to modify this procedure.
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IBM System Storage DS3950 Storage Subsystem: Installation, User’s, and Maintenance Guide