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<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>I concur. We did some I/O benchmarking using a 24
drive server, I think it was this server <a
href="http://supermicro.com/products/chassis/4U/846/SC846E1-R900.cfm">http://supermicro.com/products/chassis/4U/846/SC846E1-R900.cfm</a>
with 24 15K SAS drives.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>The benchmarking was random reads and random writes
of varying sizes (multi-gig to make sure it was beyond the total cache
available).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>RAID0 = fastest (just for fun and to set the
watermark)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>RAID10 = second fastest (about 65% of RAID0)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>RAID5 = a very very distant last (about 20% of RAID0)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>These % numbers are rough and from memory of several
weeks ago. It is combined read and write performance.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>We also had two 4-gig iram drives in a RAID0, wow
that is fast!! <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
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<p class=MsoNormal><b><font size=2 color=black face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:windowtext;font-weight:bold'>From:</span></font></b><font
size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'> tclug-list-bounces@mn-linux.org
[mailto:tclug-list-bounces@mn-linux.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Chris Barber<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, May 28, 2008 3:58
PM<br>
<b><span style='font-weight:bold'>To:</span></b> tclug-list@mn-linux.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [tclug-list] OT -
Hardware Advice</span></font><font color=black><span style='color:windowtext'><o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>It would be insane to hook up 12 drives in a
RAID5. If you lose a drive, it's gonna take a day to rebuild the array
and what happens if you lose a second drive while you're rebuilding? 4 x
250GB drives in RAID 5 took about 10 hours to rebuild. It is probably
quicker to format and re-install. I hope you have backups.<br>
<br>
I use RAID 1+0 for database servers. For a app, file, or mail server, I
do RAID 1 unless I needed the space, then I'd do RAID 6. I don't run RAID
5 on any of my servers anymore because I need redundancy beyond losing 1 drive
and the write performance blows.<br>
<br>
I should note that you can get sufficient performance from a RAID 5/6 by using
a controller with 256MB of cache and allocated most of it to write-back cache.
Also, you should have a lot of RAM to cache database pages in RAM and cache
queries to avoid hitting the disk.<br>
<br>
-Chris<br>
<br>
<br>
Bret Baptist wrote: <o:p></o:p></span></font></p>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>On Wednesday 28 May 2008 1:47:32 pm Josh Paetzel wrote:<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'
id="StationeryCiteGenerated_1" type=cite><pre wrap=""><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt'>On Wednesday 28 May 2008 11:14:50 am Justin Krejci wrote:<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'
id="StationeryCiteGenerated_2" type=cite><pre wrap=""><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt'><a
href="http://download.intel.com/support/motherboards/server/srcsas18e/sb/axxrpc">http://download.intel.com/support/motherboards/server/srcsas18e/sb/axxrpc</a><o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>m2 _ tps_10.pdf<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Benefits are identified in this PDF.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Data caching (write-back cache can greatly improve write performance)<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Busy databases servers commonly need lots of I/O<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Also consider running RAID10 if you have drive availability (4 drive<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>minimum) as you will get much higher I/O performance with that as well<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>especially with writes. Though if you need the capacity, RAID5 will give<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>you one drive more of capacity. RAID10 can also give you a smaller chance<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>of data loss due to drive failures as you can potentially lose up to half<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>of your drives and still operate whereas using RAID5 and losing 2+ drives<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>= disaster.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre></blockquote>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>Somewhere a DBA just rolled over in his grave at the mention of a database<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>using RAID 5. If you're ever going to care about performance at all don't<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>use RAID 5. It's particularly slow at the sorts of write I/O database<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>systems typically generate.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre></blockquote>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>For the most part this is true, however on a lot of modern RAID controllers if <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>you hook 12 drives up in RAID-5 you are going to see amazing performance. <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Here is an article with a very thorough review of 9 SATA RAID cards:<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><a
href="http://tweakers.net/reviews/557/26/comparison-of-nine-serial-ata-raid-5-adapters-pagina-25.html">http://tweakers.net/reviews/557/26/comparison-of-nine-serial-ata-raid-5-adapters-pagina-25.html</a><o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>The issue here is that they do not do a RAID-10 test with 12 drives.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>I don't know what they are doing on the Coraid SR 1521 to make RAID-5 faster <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>than RAID-10, but when you get up to 14 drives in the chassis you get much <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>better throughput, now mind you this is not random I/O, just another thing to <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>think about:<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><a
href="http://coraid.com/support/sr/ANSR002.pdf">http://coraid.com/support/sr/ANSR002.pdf</a><o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>For a large number of drives in a RAID-5 you get really good performance and <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>much higher capacity. <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Not that this is really relevant to the original poster.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Thanks.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'> <o:p></o:p></span></font></pre>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
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