that is not easy
The management of RAID arrays in the kernel is a complicated task - and one
upon which the fate of much data relies. Given that, it would make sense
to have a single set of RAID routines which is improved by all. What the
Linux kernel has, instead, is three different RAID implementations: in the
multiple device (MD) subsystem, in the device mapper (DM) code, and in the
Btrfs filesystem. It has often been said that unifying these
implementations would be a good thing, but
and thus far,
it has not happened.
MD maintainer Neil Brown has now taken a step in this direction with the
posting of his dm-raid456
module, a RAID implementation for the device mapper which is built on
the MD code. This patch set set has the potential to eliminate a bunch of
duplicated code, which can only be a good thing. It also brings some nice
features, including RAID6 support, multiple-target support, and more to the
device mapper layer.
This is early work which, probably, is not destined for the next merge
window. The response from the device mapper side has been reasonably
positive, though. So, with luck, we'll someday have both subsystems using
the same RAID code.
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