CX3-80 with VMware

[aspect75]

Hi,

I'm new to SAN and our co. is in the process of planning VMware vSphere with EMC CX3-80.

Whats the best RAID5 configuration for the CX3-80 DAE's and secondly we want to get the best performance across the DAE's for disks and we were thinking of setting up 2 RAID5 groups on each DAE and then using metaLuns across 3 DAEs. THis way we can get the best performance and spread the processing across the various SPs on each DAE.

Can anyone give me some advise on this setup?

 

[mrdenny]

How many VMs are you going to be running? How much IO do you expect them to need? Most VMs, unless they are running something like Exchange, SQL, etc need very little IO.

For example I've got about 50 guests running on my ESX hosts. I've got two 5 disk RAID 5 arrays built with 3 LUNs on each array. All the guest OSs are on these 6 LUNs. For the data drives for the VMs I've got 3 more RAID 5 arrays (also 5 disks each) with 2 LUNs in each RAID group.

The only thing which isn't stored on these LUNs are the Exchange volumes which are presented to the guests via iSCSI (we have a CX4 which has iSCSI built in).

Unless you are expecting a very high amount of IO (or a ton of guest machines), the config you are looking at will be more than enough.

Denny
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[NickFerrar]

We use 300GB or 450GB 15k FC drives in our Clariions for VMware and generally create a RAID 5 groups of 4-7 drives with a single LUN in each for the VMFS LUN. What works for you does depend a lot though on what's running on your VMs.

 

[xmsre]

vSpere does quite a bit of read caching before the IO hits the array. By the time the IO gets to the array, it's a random IO pattern with about a 1:1 R/W ratio.

RAID 5 is optimized for reads. The write performance sucks in comparison. The industry rule of thumb is "If the write penalty of your proposed RAID type is higher than the R/W ratio of your application, then your proposed RAID type is a poor choice". RAID 5 has a write penalty of 4. RAID 10 has a write penalty of 2. You decide.

XMSRE