What is the most IOPS one can expect from an EMC Clariion CX300?

We are currently using a CX300 for vmware and exchange 2007 and are trying to get the most out of our current investment in terms of performance.  We have four shelves available with different drives, 1) 15 x 146gb 10k, 2) 15 x 73gb15k, 3) 15 x 300gb 10k, 4) 10 x 500gb 7.2k.   What could be done within a single shelf or even two shelves to get the highest IOPS?

Thank you,
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Duncan MeyersCommented:
First up, don't put any VMware workloads on the ATA drives. That way madness lies.

A 10K rpm drive gets about 140 IOPS, 15K about 180 IOPS - so about 4200 IOPS in 10K drives and 2700 IOPS from the 15K drives. You only need two FC hot spares - a 300G and 146G would be the best choices. The ATA drives require their won hot spare.

The way you configure the array depends on which are the OS drives (drives 0-4 in the main cabinet) as you lose 6GB off each OS drive. To get the best possible IOPS, I'd configure the first shelf as 3 4+1 RAID 5 groups and FC shelf 1 and 2 as two sets of 6+1 RAID 5 each plus a hot spare. You could go with an 8+1 RAID 5 set for the ATA drives and a hot spare.

Next step is to configure LUNs. Assuming you are using 500GB VMFS partitions, on the first pair of 6+1  groups, create 250GB LUNs and use striped metLUNs (LUN expansion) to stitch the LUNs together (250GB + 250GB = 500GB). For the OS shelf, use 3 x 166GB partitions and striped metaLUNs. The advantage of metaLUNs is that you get the benefit of writing across as many drives as possible without the disadvantages of extremely long rebuild times.

Create the VMFS partitons through VirtualCenter and the alignment offset will be created correctly, but you should also align any LUNs (D: drives and so on) using the conventional Windows or Linux methods.

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Duncan MeyersCommented:
You can make a CX300 fly if you lay it out right. The downside is you can't expand it any further. The CX300 maxes out at 60 drives.

If the CX300 is going to be coming out of maintenance soon, check out the new CX40-120 - it supports up to 120 drives and you'll find maintenance enewal will go a long way to buying a brand-new box.

One last thing - set your read cache to about 25MB and max out write cache.
timdinsdAuthor Commented:
We also have a CX700 that we can use, would we see a big improvement in performance going to that?  Thank you for the fast and thorough response!
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Duncan MeyersCommented:
The CX700 has more processor oomph and more write cache, but the most important thing you can give VMware is lots and lots and lots of disk spindles. I very much doubt you'll see much of a difference unless you have a BIG environment. If the CX300 keeps hitting write cache forced flushes, it means that you need more disks - and the same applied to a CX700. A CX700 has more cache, so it will take a bit longer to saturate it, but the same rule applies. Forced write cache flushes = buy more disk.
timdinsdAuthor Commented:
Meyersd is definitely an authority on matters of storage, just read his many responses to storage related questions.  Extremely helpful.
Duncan MeyersCommented:
Thanks! Glad I could help.
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