Ubuntu Server and software RAID


Well-Known Member
I previously posted that I wanted to setup a server with RAID. I did that but settled on a non-server desktop install. The hardware's a bit old and was having trouble getting things to cooperate. I have 1 TB disks that I partitioned into 2 slices, 1 for the OS (no Raid) and 1 on all 3 for Raid 5. My goal is to be able to reinstall the OS and reclaim the RAID rather than recreate it and have to do a restore. I've been able to do this using the desktop distro. I want to overwrite the OS with Ubuntu Server, but I don't think I can reclaim the RAID. At the point where you setup the disks it seems to me that you can't pick existing partitions like you can during desktop installations. You can only create new ones. I thought maybe just create the OS partition, but I'm concerned that if I go 1 MB over the existing, it'll ruin my raid partition. Does anyone have experience with this or know where I can find out more on it?



Active Member
Normally RAID is based on physical disks. Not partitions on a disk. It's kind of an "all or none"
type of thing. I'm assuming these are spindle/platter disks, not SSD's. You can't spin half a platter.
I think the desktop distro might have been fooled into thinking it was a separate disk.
Most distro's these days are smart enough to the know the difference.

I know you want to recover the data, (I would probably try a "live CD") and see if I can copy the data off someplace temporarily. If you want to use RAID, make the whole disk part of the RAID.
(Are the disks, all the same make and model?) If the disks are different sizes (even just a few MB)
the RAID will shrink all your disks to the size of the smallest one.

i.e. If you have 2 1TB disks, and 1 900GB disk, the RAID will treat them all as 900 MB.
You said you were able to do this with an older desktop distro. Is this a live CD?
Can you boot from it and see the partitions?

If you decide to keep going with RAID, you need to use the entire disks.
If you want to keep the OS separate, I would go with RAID 1 on two of the disks (mirroring)
and not use RAID at all on the OS disk. If you decide to go RAID 5 across all 3 disks, you will have
to have the same partitioning scheme on all of them (the RAID takes care of this automatically)

Another option I usually use on RAID stripes, is LVM. That way I can make the partitions any size I want on the fly. I can add new partitions on the fly. If you're going to changing OS's from time to time,
leave some space for a new OS partition, and you can always delete the old OS partition later.


Well-Known Member
While I don't disagree with you that normally raid uses entire disks and my setup isn't optimal, Ubuntu Server should still be able to see existing partitions. Whether they're partitions for RAID or whether they're partitions for OS installations. In the picture I attached, to the posting, you can't even see the OS partition.


Well-Known Member
I bought a SATA 3 card, the computer only supported SATA 2, and an SSD card. I installed Ubuntu server on it, but found some of the remote administration a bit tough, so I overwrote that with Kubuntu. Oddly, Kubuntu didn't recognize any partitions on teh HHDs either. I created new and am setting up the RAID on them now. Crossing my fingers that if anything happens to the OS that the RAID will be recoverable. Of course I'll have to figure out how I'm going to do backups so that if there is trouble, it won't be permanent.

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