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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Well, as far as I know the amount of IOPS you can get from a RAID 5/6 is the same that you get from a single disk. The write can not be acknowledged until it
is written to all the data and parity disks.<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">With regards it scaling beyond 16 disks, yeah it might do and be possible to create with more disks, however it might increase the rebuild time when a disk
gets replaced and in theory it should decrease performance as there will be more disks to acknowledge writes.<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">Fernando<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"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> George Machitidze [mailto:giomac@gmail.com]
<br>
<b>Sent:</b> 14 June 2012 14:01<br>
<b>To:</b> Fernando Frediani (Qube)<br>
<b>Cc:</b> gluster-users@gluster.org<br>
<b>Subject:</b> Re: [Gluster-users] RAID options for Gluster<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi,<br>
<br>
Some corrections...<o:p></o:p></p>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm">
<p class="MsoNormal">Cons:<br>
Extra cost of the RAID controller.<br>
Performance of the array is equivalent a single disk + RAID controller caching features.<br>
RAID doesn’t scale well beyond ~16 disks<o:p></o:p></p>
</blockquote>
<p class="MsoNormal"><br>
Performance of the array is not equivalent of a single disk and doesn't depend only on cache size or spec. features - it depends on the total IOPS, block sizes, access type etc.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">RAID scales well beyond 16 disks, ex. for Adaptec. Yes, it will scale, but is it software or hardware, for both array reconfiguration and grow is the same kind of problem - data needs to be reallocated.<br>
<br>
Maximum Number of Arrays that can be created on the same set of drives: 4<br>
Maximum Logical Drive Size: 512TB<br>
Maximum Number of Drives in Striped Array (such as RAID 0): 128<br>
Maximum Number of Drives in RAID 5 Array: 32<br>
Maximum Number of Drives in RAID 50 Array: 32<br>
Maximum Number of Drives in RAID 6 Array: 32<br>
Maximum Number of Drives in RAID 60 Array: 32<br>
Available Stripe Sizes for Arrays are 16, 32, 64, 128, 256, 512, or 1024 KB. Striped RAID configurations have a default stripe size of 256 KB.<br>
Note: A RAID 10, RAID 50, or RAID 60 array cannot have more than 32 legs when created using the Build method. Maximum disk drive count is only limited by RAID level. For instance:
<br>
a RAID 10 array built with 32 RAID 1 legs (64 disk drives) is supported<br>
a RAID 50 array built with 32 RAID 5 legs (number of drives will vary) is also supported<br>
<br>
<br>
Best regards,<br>
George Machitidze<br>
<br>
<br>
On Thu, Jun 14, 2012 at 3:06 PM, Fernando Frediani (Qube) <<a href="mailto:fernando.frediani@qubenet.net">fernando.frediani@qubenet.net</a>> wrote:<br>
> Cons:<br>
><br>
> Extra cost of the RAID controller.<br>
><br>
> Performance of the array is equivalent a single disk + RAID controller<br>
> caching features.<br>
><br>
> RAID doesn’t scale well beyond ~16 disks<o:p></o:p></p>
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