IBM DS3500 Installation, User's, And Maintenance Manual page 145

1. Instructions that are provided with the software supersede any instructions and
information in this document.
2. Use "Hard disk drive locations" on page 183 to ensure that you replace the
drives into the correct bays.
Attention: After you remove a drive, wait 70 seconds to allow the drive to spin
down before you replace or reseat the drive. Failure to do so might cause
unpredictable results.
There are two methods for upgrading drives:
v Replacing all the drives at the same time
This method requires that you back up the data on the affected drives and then
turn off the DS3500 storage subsystem.
Attention: Turn off the DS3500 storage subsystem before you turn off the
attached storage enclosures.
After you replace all the drives, you must reconfigure the new drives and
restore data from backup. See the procedure in "Replacing all drives at the same
time" on page 128.
This is the safest way to exchange drives 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 enclosures attached to the storage
subsystem) until you finish the procedure. You must use this method on RAID 0
logical drives.
v Replacing the drives one at a time
In this method, you manually fail each drive, replace it, and wait for the system
to restore data to the new drive before you install the next drive. After you
install the new drives, you can configure them to make the additional drive
space available. See the procedure in "Replacing the drives one at a time" on
page 130.
Using this method, you can replace the drives while the storage enclosures and
the DS3500 are running, eliminating the downtime that is required if you replace
all the drives 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, 5, or 6). You cannot use this
method with any drives that contains 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 drive
malfunctions.
The method that 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 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 drives.
v The number of drives in an subsystem. Replacing drives one at a time is better
suited to subsystems that consist of three to five drives. If you have more than
10 drives, consider replacing all drives at the same time.
Chapter 5. Replacing components
127