mrmagoo wrote:
I have a question about RAID+LVM I honestly couldn't understand. I'm
assuming you are using RAID5 or some other kind that can't be resized;
what is the benefit of using an LVM on such? From what I read, the
LVM would be set to md0 and if you wanted to add another drive you'd
need to add a new md device, aka 3+ more drives and a lost drive's
worth space.
So, in this kind of case, is there any point of even using it?
I just recently lost 250x4 in a RAID5 due to 1 drive failing and the
filesystem on another drive getting completly corrupted. I'm still
not sure what happened, but the SATA controller went poof and I think
heat is to blame (my fault). I'm still at a loss as to what
filesystem I should use, but was leaning twords XFS.
1) RAID[1/5/10/...] protects against (1) disk failure, not against
controller failure. Nor does it protect against user error (for example
not providing enough cooling, or deletion of files). When the controller
goes, only a backup on a separate controller/system will help.
2) Many RAID5 solutions support growing the RAID. Some by changing to
larger disks (development in linux SW RAID), many HW RAID solutions
support growing by adding disks to the set.
3) LVM over RAID makes it possible to add disks (single, RAID set, .. )
to the LVM set.
This said, I have data i do not like to loose on RAID1 or RAID5 sets.
Data i hate to loose, gets a nightly backup to a different system (which
has its own RAID set for the most important data). As somebody else has
remarked, i've seen too many dead disks.
Cheers,
Rudy
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