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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Yeah, that’s right – <o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>You did say PE 2950, and you also said raid controller only
supports 0 or 1. This is almost certainly false. You have the PERC 4, 5, or
6, right? These all support Raid 5. Which is a clear choice over 0.<o:p></o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> bblisa-bounces@bblisa.org
[mailto:bblisa-bounces@bblisa.org] <b>On Behalf Of </b>Rick Pike<br>
<b>Sent:</b> Thursday, March 06, 2008 11:41 PM<br>
<b>To:</b> bblisa@bblisa.org<br>
<b>Subject:</b> Re: [BBLISA] Moving from RAID 0 to LVM RAID?<o:p></o:p></span></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'>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.<br>
<br>
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.<br>
<br>
Rick<o:p></o:p></p>
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<p class=MsoNormal>On Thu, Mar 6, 2008 at 6:58 PM, Scott R. Ehrlich <<a
href="mailto:scott@mit.edu">scott@mit.edu</a>> wrote:<o:p></o:p></p>
<p class=MsoNormal>So I've learned a valuable RAID 0 lesson, and it fortunately
was not a major<br>
catastrophy. I got lucky, and had a workable-enough backup on tape to
make the<br>
user who needed some data happy.<br>
<br>
Now, from the OS side, LVM is an option. Say the RAID controller only
allows<br>
hardware striping or mirroring for logical volumes, but I want to use more than<br>
two disks, and I don't want the RAID 0 problem again.<br>
<br>
When I get a replacement disk and build the system from the ground up again, I<br>
could, conceivably, use hardware RAID 1 for the OS on two disks, and CentOS 5<br>
64-bit's LVM for software RAID 5 (or maybe 1+0 if available) on the remaining<br>
for 4 disks, maybe 3 disks as active and the 4th as a hot spare?<br>
<br>
I've never had much faith in software raid, since it is not hardware-based, and<br>
there would be a performance hit, but in this case, it could be an option.<br>
<br>
Insights from the OS-created RAID experience welcome.<br>
<br>
Thanks again.<br>
<br>
Scott<br>
<br>
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