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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hardware vs Software RAID? That’s a no-brainer. Do it in
hardware, let the computer CPU work on more important things.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>PE2950: Doesn’t come by default with the PERC. You have to
specify it when ordering. It’s possible, though doubtful, that the server in
question does not have the hardware RAID card in it.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<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>Edward
Ned Harvey<br>
<b>Sent:</b> Friday, March 07, 2008 8:16 AM<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><o:p> </o:p></p>
<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>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
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>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><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><o:p> </o:p></p>
<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>
<div>
<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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