Greetings,
There seem to be two ways of doing software RAID, and I have had trouble
finding information on this.
First, the raid is done with partitions, for example /dev/sda1 and
/dev/sdb1 are partitioned as Linux type and the mirroring is done then
between the two partitions. The writing takes place on a filesystem
level, and the partition table is not actually mirrored, because it's
not on /dev/sda1 or /dev/sdb1.
The hardware raid does the mirroring on the block level, so it's
actually /dev/sda mirroring /dev/sdb - the whole drive, and not
partitions. There is a way to set this up on software raid. It takes
more configuration tweaking, but the mirroring then includes the
partition table as well. This way, if a drive fails, one can replace it
without pre-partitioning it.
This also raises another point, which is relevant for both cases - same
exact models of hard disks have different number of cylinders, so if a
RAID partition is created on a larger drive it cannot be mirrored to a
smaller drive.
Does anyone have any experience with this?
A.
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