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Attention:
After you remove a drive CRU, wait 70 seconds before replacing or
reseating the E-DDM CRU to allow it to properly spin down. Failure to do so may
cause undesired events.
The following are methods for upgrading E-DDMs:
v Replacing all the E-DDMs at the same time
This method requires that you back up the data on the affected E-DDMs and
then turn off the EXP810 and the DS4000 storage subsystem.
Attention:
Turn off the DS4000 storage subsystem before you turn off the
EXP810.
After replacing all the E-DDMs, you must reconfigure the new E-DDMs and
restore data from backup. See the procedure in "Replacing all E-DDMs at the
same time" on page 98.
This is the safest way to exchange E-DDMs without losing data. However, this
method might take a long time to complete because of the backup,
reconfiguration, and restoration processes. In addition, other users are not able
to use the storage subsystem (or any storage expansion enclosures attached to
the storage subsystem) until you finish the procedure. You must use this method
on RAID 0 logical drives.
v Replacing the E-DDMs one at a time
In this method, you manually fail each E-DDM, replace it, and wait for the system
to restore data to the new E-DDM before installing the next E-DDM. After you
install the new E-DDMs, you can configure them to make the additional E-DDM
space available. See the procedure in "Replacing the drives one at a time" on
page 100.
Using this method, you can replace the E-DDMs while the EXP810 and the
DS4000 are running, eliminating the down time that is required if you replace all
of them at once. However, this method is more risky because you can lose data
if the drive restoration or storage subsystem reconfiguration process fails. In
addition, the reconstruction process might take a long time. This method works
only on redundant logical drives (RAID 1, 3, or 5). You cannot use this method
with any drives containing RAID 0 logical drives.
Consider backing up your data if you use this method. This safeguards your data
if the restoration and reconfiguration process fails or the new E-DDM
malfunctions.
The method you use depends on the following considerations:
v Which method most closely matches the recommended drive upgrade procedure
that is provided 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 drives 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,
consider replacing all of them 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 an E-DDM 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.
Chapter 5. Installing and replacing components
97
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