RAID and Linux

[Lennart Sorensen]

On Thu, Jan 31, 2008 at 12:10:42PM -0500, William O'Higgins Witteman wrote:
> I have inherited a Dell PowerEdge 6800, and I'm about to put Linux
> (Debian) on it.  It has three drives right now, but I am likely going to
> want to add drives in the future.  I plan to use RAID 4 or 5, and I want
> to set it up so that I need to do as little as possible to add more
> storage.

I haven't used software raid5, but I believe it supports adding devices
later.

> Are there any caveats or gotchas I should be aware of?
> 
> I started an installation to see what it said about the HD, and it shows
> a single SCSI MegaRaid device of 270ish Gb, which fits with what I know
> of RAID 4/5 for three 146Gb disks.  I've never used RAID before, and I
> don't want to paint myself into a corner.  Thanks.

Well if you use hardware raid then it isn't up to linux to support
adding to the existing raid, it depends on the raid controller.  Some
support expanding a raid5, some do not.  The only one I have worked with
was an ibm serveraid which certainly did support expanding the raid with
extra drives later.  I used that feature a few times.  Personally I
would rather use linux software raid since the performance for raid1
certainly dropped significantly moving from linux software raid to the
ibm serveraid 4m with the same disks.

--
Len Sorensen
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