Novell LINUX ENTERPRISE SERVER 11 - STORAGE ADMINISTRATION GUIDE 2-23-2010 Administration Manual page 97

RAID Type
RAID 1
RAID 4
RAID 5
RAID 6
To create a degraded array in which some devices are missing, simply give the word
place of a device name. This causes
When creating a RAID 5 array,
drive. This is because building the spare into a degraded array is generally faster than
resynchronizing the parity on a non-degraded, but not clean, array. You can override this feature
with the option.
--force
Creating a degraded array might be useful if you want create a RAID, but one of the devices you
want to use already has data on it. In that case, you create a degraded array with other devices, copy
data from the in-use device to the RAID that is running in degraded mode, add the device into the
RAID, then wait while the RAID is rebuilt so that the data is now across all devices. An example of
this process is given in the following procedure:
1 Create a degraded RAID 1 device
following at the command prompt:
mdadm --create /dev/md0 -l 1 -n 2 /dev/sda1 missing
The device should be the same size or larger than the device you plan to add to it.
2 If the device you want to add to the mirror contains data that you want to move to the RAID
array, copy it now to the RAID array while it is running in degraded mode.
3 Add a device to the mirror. For example, to add
the command prompt:
mdadm /dev/md0 -a /dev/sdb1
You can add only one device at a time. You must wait for the kernel to build the mirror and
bring it fully online before you add another mirror.
4 Monitor the build progress by entering the following at the command prompt:
cat /proc/mdstat
To see the rebuild progress while being refreshed every second, enter
watch -n 1 cat /proc/mdstat
Allowable Number of Slots Missing
All but one device
One slot
One slot
One or two slots
to leave the corresponding slot in the array empty.
mdadm
automatically creates a degraded array with an extra spare
mdadm
, using one single drive
/dev/md0
/dev/sdb1
Managing Software RAIDs 6 and 10 with mdadm
missing
, enter the
/dev/sd1
to the RAID, enter the following at
in
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