ESX Cluster: RAIDs, LUNs, Setup

SCHADC
SCHADC used Ask the Experts™
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Hi,
Planning to setup an ESX 3.5 Cluster with the following hardware:
Step 1:
SAN: DELL MD3000i 15x 600GB 15K
SRV1: DELL R710 / 6x 450GB 15K HDD; 72GB RAM; 8xNIC, 2xQuadCore

Step 2:
SRV2: DELL PE2950II / 6x 450GB 15K HDD; 48GB RAM; 6xNIC, 2xQuadCore (on this server I already have an ESX 3.5 with about 8 VMWares running successfully)

Notes:
About 30 win servers will run on this environment no Exchange, no Oracle, no other DB
SAN and Srv1 are already iSCSI connected (isolated LAN)

Questions:
1.      Best RAID setup for the SAN? (I thought of Raid5 Disk 0-4; Raid5 Disk 5-13 and hotspare Disk14, does it make sense?)
2.      How many LUN’s and what size?
3.      After finishing step1 how do I best handle the step2?
4.      Though the storage from the SAN is enough for my VMWares needs, how can I best use also the internal storage from the servers?

Many thanks in advance
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Question 1: why 3.5 when 4 is available (i'm assuming you'r re-using licenses

1. Sounds perfectly sensible. Have you considered 4,4,3,spare?
2. Primary aim is to reduce contention on the luns.

we run our VM hosts with (multiples of) 3 luns. System,Page,Data/apps. Anything needing low latency we run as RDMs. Page file vdisks tend to be smaller than system and data disks (so might be better targetted at a smaller lun, for example the 3 disk set

we keep the lun sizes to about 200GB each. If more space is required, we add additional luns

to summarise, that's each vm with 3 vmdks, each vmdk on a separate lun, each lun on a separate set of spindles.

3. Assuming you're licensed, i'd recommend installing virtualcentre (on a vm is perfectly acceptable and workable, even though it sounds like a silly idea the first time you hear it) and adding both systems into it. Create a data centre, and a cluster within the datacentre,  and drop both hosts into it. This is the required configuration if you want to take advantage of vmware HA.  This system should function quite nicely. If you don't have licences which cover HA, you could drop the servers straight into the datacentre.

You might need to check out CPU compatabiltiy if they don't exactly match. - especially if planning to use any of the advanced features like Vmotion, DRS. I believe you can use CPU masking to cover over any cracks in compatibility

Regards

Author

Commented:
Thanks Ignatius, I'm licensed for 3.5 that's why not ESX4
1. I was told 5 and 9 disks give the best performance in RAID 5
2. My VMWares are gonna be about 60-100GB each so I don't think 200GB LUNs will fit. I was thinking to make 1.5-2TB but I don't know if it's resonable regarding perfrmance
3. What about the VMWares already running on the SRV2?
4. how can I best use also the internal storage from the servers?

Thanks again
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Hi.

1. I've never heard this before, but if you have it from a reliable source I'm not going to argue.

2. For VMs that seems very large. The OS doesn't need to take more than about 10-12GB (20GB x64). I have to assume the rest is mostly data. Performance would depend on concurrent access to the lun If you're doing a lot of intense access to the data, keep the luns a lot smaller than that. That's why I recommend a separate lun for page files.

You might even consider using an RDM for the data if you need a lot of io, which would give you no contention at the lun level (use a virtual RDM to increase flexibiility). If the data is stored for long-term archiving purposes then the actual size of the disk is not really important

3. When you add server 2 into virtualcenter, the VMs should stay running - or are you planning to rebuild this box? - you don't say.

4. Internal storage can be allocated as VMFS, however it's not suitable for any enterprise features like HA, DRS. Probably best used for test boxes or storage of ISOs - things you can afford to lose in the case of a server failure
PS - with RDM, you present a lun to ESX, but don't configure it as a filesystem, you then connect it straight to the VM as an external disk and format it. It relies on a 'stub' vmdk file which redirects access to the lun.

I just thought again about Q3 - i think you're saying these VMs are on the local disk and you want them on the SAN,

This can be done in 3 ways:

1) If you're licensed for vmotion, you could use storage vmotion to migrate them to the new storage (storage vmotion is done from the esx command line tools (not pretty) or using a third party plug-in to vc. This should involve no down-time for the vm.

2) if not, then you can stop the vm, right-click it and select "migrate" - just follow the wizard. (if you have multiple disks, you can select multiple destinations if you use the advanced button on the disk screen)

3) i've seen people use vmware converter for this - to effectively make a copy of the vm. Seems like overkill, but the option is there


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