[BBLISA] Moving from RAID 0 to LVM RAID?

[Rick Pike]

You didn't give much detail about the hardware, but you mentioned a PE2950
which I assume is Dell Power Edge 2950. I worked with some of these last
year and our standard storage configuration was 4 internal disks configured
as a single RAID 5 volume using the embedded RAID controller. Actually what
I had recommended was 6 smaller internal disks for the same price.

The RAID 5 provided an acceptable balance between capacity, protection, and
performance. We did some minimal testing to see if reconfiguring the same
hardware with mirroring (was it 2 RAID 1 volumes or 1 RAID 1+0 volume?)
would provide a performance boost (at the expense of capacity), but we did
not notice an meaningful difference in our application. Your mileage may
vary.

Rick

On Thu, Mar 6, 2008 at 6:58 PM, Scott R. Ehrlich <scott at mit.edu> wrote:

> So I've learned a valuable RAID 0 lesson, and it fortunately was not a
> major
> catastrophy.  I got lucky, and had a workable-enough backup on tape to
> make the
> user who needed some data happy.
>
> Now, from the OS side, LVM is an option.   Say the RAID controller only
> allows
> hardware striping or mirroring for logical volumes, but I want to use more
> than
> two disks, and I don't want the RAID 0 problem again.
>
> When I get a replacement disk and build the system from the ground up
> again, I
> could, conceivably, use hardware RAID 1 for the OS on two disks, and
> CentOS 5
> 64-bit's LVM for software RAID 5 (or maybe 1+0 if available) on the
> remaining
> for 4 disks, maybe 3 disks as active and the 4th as a hot spare?
>
> I've never had much faith in software raid, since it is not
> hardware-based, and
> there would be a performance hit, but in this case, it could be an option.
>
> Insights from the OS-created RAID experience welcome.
>
> Thanks again.
>
> Scott
>
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