Re: how easy to recover RAID5?

mechphisto@xxxxxxxxx wrote:
I'm looking to RAID5 together about three 600GB drives, using Fedora
Core (7 at the moment, but I anticipate using 8). (Come to think of
it, we may end up using CentOS. Either way....)

I found how it's easy to set up a software RAID5 using Disk Druid.
Lots of pros and cons regarding the different RAIDs. But, I'm having
trouble finding information on how to recover a RAID 5. I don't want
to irrevocably tie our data into three drives if something "bad"
happens to one, I can't easily restore.

I take it of one of the three drives goes out, the entire array is
unusable until the drive is replaced, right?

Nope. In fact, you never know if you don't check /proc/mdstat - or use something like logcheck or mdadm to email you a warning that you just dropped a drive. (I've had drives go down and take the bus with them but that's atypical.)

But then what? You pop in
a new drive, boot up--something automagically happens to recover the
data and redistribute bytes onto the new drive? Or do I have to boot
up with Knoppix/FC console disk and run something?

Not quite. You drop in a replacement drive (depending on your hardware you may have to shut down, or whatever), fdisk the drive to set up the partitions, and then run mdadm and tell it to rebuild whatever partitions you lost.

man mdadm
google for a recent raid howto
.

Relevant Pages

  • Re: Replacing a raid 5 controller with different card
    ... at least for the part not depending on S-ATA or the RAID ... drives present to the OS at the bios level. ... raid controller and you make an array based on the number of drives ... In the operating system you make partitions. ...
    (microsoft.public.windows.server.sbs)
  • HELP Recover software RAID5...
    ... I am hoping some brilliant sysadm can help me recover my software raid 5. ... Over Time as the media drive was filled up, I add additional drives to the ... mdadm: /dev/sdh1 requires wrong number of drives. ... mdadm: /dev/sdh has wrong uuid. ...
    (comp.os.linux.misc)
  • Re: Migrating to Raid
    ... RAID would do... ... It is unclear whether you want to migrate the two existing 200GB drives into ... I note you do not have shared partitions for /home /usr etc. in your ... server - and a cheap box for that would cost less than your RAID card! ...
    (alt.os.linux.suse)
  • Re: Mdadm -- Restoring an array
    ... past, when I've tried to restore a RAID, I've had trouble with it. ... The man page for mdadm makes it look like a RAID can be reassembled ... to tell mdadm to scan local drives and re-assemble an existing RAID. ... Of course, if a drive is replaced, you'll need to create a new conf file. ...
    (Debian-User)
  • Re: Installing Exchange for performance
    ... > Not sure what you mean by 4 pairs of mirrored RAID drives... ... > mirroring offers better performance because of sequential writes. ... >> needs partitions for the SMTP queues, ...
    (microsoft.public.exchange.setup)