Can you change OS and retain data on software raid-5 disks?

dubcat · 20 Feb 2012 at 12:44

Hi,

I have a 250gb drive I will install an OS on, probably Ubunutu Server. I have 3 x 2TB drives I want to create a software raid-5 array out of and use XFS files system on. I would like to know if I can change the OS on the 250gb drive at a later date in time to another OS that supports software raid-5 and XFS and retain all the data on my 3 x 2TB drives.

The specific example here is going from ubuntu server to freeNAS. Both support software raid-5. Both support xfs. If I switch OS will all my data still be accessible on those data drives?

Thanks,
Dub

leezer3 · 20 Feb 2012 at 12:55

Probably

My only word of caution is that FreeNAS is a BDS derivative, as opposed to Linux, and while in theory it should work just fine, I wouldn't be trying it with 6tb of data, just in case there is something different enought to cause issues.
Software Raid-5 on 6tb isn't particularly clever either, if a drive dies you will be forever rebuilding that.

-Leezer-

SMN · 20 Feb 2012 at 12:58

Well to answer original question, if you have software RAID (MD RAID in all probability), you can mount that RAID array from within any Linux operating system (within reason, may require 2-3 mins tweaking using mdadm etc).

SMN · 20 Feb 2012 at 12:58

(For proof, I have 2 OS; Arch and Ubuntu). I build the array using disk utility in ubuntu, then booted into my new arch, opened Disk utility and mounted the array no problem. Similar story for CLI.

dubcat · 20 Feb 2012 at 21:18

leezer3 said:
Software Raid-5 on 6tb isn't particularly clever either, if a drive dies you will be forever rebuilding that.

Hi mate - what would you recommend instead of raid5 then? I have 3x2tb drives. I know if i get 4 drives i can run raid6. Would that be better? What about until then though? What alternative to raid5 under ubuntu server?

Thanks to the other folks too for your replies. I feel better that I am not locked in to one distribution. Reality is I would probably switch from ubuntu server to openmediavault rather than freenas if it all got a bit too much for me. Openmediavault is debian based too.

Now I got my head scratching about what Raid to use.

leezer3 · 20 Feb 2012 at 22:44

Sadly, no software RAID is particularly clever

A software RAID-5 array of that size will take somewhere in the region of 1-2 days to recover from a failed disk (Depends on the CPU and whether you want to use the machine in the meantime). Software RAID-6 will again take somewhere about that amount of time to rebuild, but will let 2 disks fail, not one.

Hardware RAID is considerably better in terms of rebuild times, and writes to the drives would be faster too.

In all honesty though, I tend to question the use of a RAID array in a home environment. I prefer an offsite backup of any important data (I've got a 1tb drive in a caddy that lives round my mothers, plus a cloud backup service for the documents), but just leave media drives as single disks, all mounted under /mnt/media/disk*

-Leezer-

Essexraptor · 21 Feb 2012 at 00:32

Just remember that no RAID array, hard or soft is a backup solution. Backup the data to an external source on a regular basis and you'll do just fine. Use a mixture of of physical and cloud solutions. That way you can still have access to your data when the array is rebuilding.

Are you building a stand alone server solution or do you want to build and install a large array within a desktop system?

Openmediavault is a standalone NAS solution so your thread is a bit misleading so far.

I think you need to sit down and rethink this through a bit more first

dubcat · 21 Feb 2012 at 00:48

I know what you mean. My plan is to use my current nas (2 x 1TB mirrored) to store my really important data in a resilient fashion. This basically mean turning it in to a time machine for my Mac's internal 1TB hard drive. Now since it is a time machine i can't see what the point of having a mirror there is. I may well turn the mirror in to 2TB total storage and use it to backup my laptop too as well as my parents pc (via rsync or something). I will have that local backup and then will at some point sort out an offsite backup too (either via rsync to my parents house or using crashplan, mozy or something like that).

The server I am building now is for my itunes folder plus lots of HD movies which I stream to my TV. Would not be the end of the world if i lost them but would be nice to be able to recover using Raid. If the machine was out for a while it would not kill me. Am thinking of a hardware raid controller but if I can get away with it in software I will do so.