On Sat, 11 Oct 2008 23:56:34 +0200, Bill Davidsen <davidsen@xxxxxxx> wrote:
roland wrote:
Hello,
I have a server running on RAID5, on which I would like to add a 4th
disk, with a seperated filesystem. I need to have some workspace. The
same disk could be used to replace a failing disk.
This is a spare disk, and can be used only as such. I'm not sure what
you had in mind by "seperated filesystem," but you can't install another
drive such that Linux will use the drive in two ways at once. If that
was your intent it pretty much isn't going to work, and if the spare was
deployed all data on it would be lost.
Stuart Sears explaned me howto install this disk as a hot spare, but it
looks to me a little bit to dangereous. This server is serving 20
workstations, so I need to do this without taking to many risks. I
admit to be a novice on the matter of diskmanagement. I always do
standard installation of a filesystem.
Assuming you just want to add a spare, something like this works fine:
mdadm --add /dev/md0 /dev/sdf1
Then a cat of /proc/mdstat should show the device added, running as a
spare. I did that, then failed one of the existing drives, and the array
rebuilt on the spare just fine, and I got a message from monitor mode
saying it happened and was fixed.
I have to mention that the raid5 was build with the IBM utilities on this
server x3500. So I suppose this mdadm wouldn't work. Or am I wrong?
Secondly, I need extra space only as a workarea.
That's why I thought, maybe I can:
- insert a 4th disk and add a filesystem, that isn't part of the raid5.
or
- insert a 4th and 5th disk and configure it as a raid1, to be used for
non critical applications
In case of failure of the raid5, I could could use the 4th disk to replace
the failing disk of the raid5 and let the ibm utilities rebuild the raid5
Does this makes sense?
So if someone could tell me howto do this in a simple way. I searched
the internet for a simple howto, but was unsuccessful. I have to do
this at a client in France, few hours driving
Could someone keep me from having a sleepless night?
I would test the existing array before counting on it to be okay, just
in case a bad spot developed.See the wiki (http://linux-raid.osdl.org).
Oh, and there is a linux-raid mailing list where there are lots of us
who have found problems the hard way and want to share.
--
Roland Brouwers
C.A.T. bvba
zevenbergenlaan 16
B-2660 Antwerpen
Tel: +32 3 830 3305
Mob: +32 475 443105
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