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Setting up iSCSI Storage for VMware - Promise RAID

Posted on 2011-02-23
Medium Priority
Last Modified: 2016-12-08
Hello !

I have a Promise storage with raw storage of 9x2tb. I am planning to use vmware essential plus with two ESX hosts. These ESX hosts will be in High Avaliability mode. There wil be 2 Windows Servers installed as VMs.

What is the industry standard on configuring the san giving that vmware can only address 2tb datastores.

Also, I am not sure what RAID configuration wil be appropriate. Is there any recomandation?
Thank you!
Question by:itconsultant1
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Expert Comment

by:Neil Russell
ID: 34964718
The raid config I would go with 5. Create one array but segment into 3 seperate LUNS of ~=2TB

The exact choice of RAID is open to debate but I prefer to use 5 for iSCSI with VMWare.
LVL 124
ID: 34964775
RAID 5 or RAID 10 for performance.

I woulkd recommend that you carve LUNs on your storage, that are between 500 and 800GB.
LVL 37

Expert Comment

by:Neil Russell
ID: 34964906
Why so small on the LUNs?
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Author Comment

ID: 34964927
One note here. I was told that having one Array is not  a good idea. Promise technology advised to have at least 2 RAID for better performance and and failure avoidance.

If you separate that one suggested Array into 3 LUNs of 2TB you will still have a lot of free space to allocate. In addition, I believe having 2TB disk for one OS is a little bit to much.

Also, does this make sense to create one array for OSes and one Array for data? Does that make a difference?

I thought about creating 0.5 TB logical drives either by using RAID5 or RAID1.

As far as RAID. They do not have a great capacity requirement. 2TB of data should be enough.
LVL 124
ID: 34964965
Very Large datastores are a very bad idea, if they get corrupted, also if you use them for multiple VMs, the performance of the LUN degrades.

Small datastores is better.

If are using iSCSI softwqre initiator, also consider the use of Jumbo Frames, if you networking equipment and SAN supports it, you'll get much better performance.

Author Comment

ID: 34965090
Yes, that is what I was told. Also, my switches and SAN supports Jumbo frames. Please note however that I have 2TB hard drives. Which would project over 10TB of data. Therefore I would have 20 disks which is much more then I will ever need.

Ideally I would like to have :

4x OS disks about 500GB - 800GB
 3-4 x DATA disks. probably a max of 2TB.
LVL 124
ID: 34965204
OS disks of 500 - 800GB seems very large?

VMware Virtual Machine maximum disk size is 2TB minus 512 bytes.

VMware ESX lun maximum size is 2TB minus 512 bytes.


Author Comment

ID: 34965377
OS disks of 500 - 800GB seems very large?

I think it is quite large, but I have 8x2TB that I have to allocate in some meaningful form. That is why I posted this problem.

What would you recommend for the OS on the storage.
Does size matter here?
What RAID (how many hard drives) would you recommend for the OS?
What RAID and how many hard drives for DATA?

LVL 124

Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 1000 total points
ID: 34965464
Is this a SAN you have?

What's the model, I'll check the specs?

Usually, you create a RAID set with all your disks, as RAID 5 or RAID 10, with all 9 disks, so total RAW storage is 18TB raw. This is an aggreate, virtual disk (different vendors call it different things).

You then carve up this storage aggreate into volumes (luns), that get presented as datastores to the ESX Servers. e.g. 500 - 800GB LUNs.

Then you create your Virtual Machine's normally based on the requirements you have.

If you have a requirement for

800GB OS Disk (C Drive)
2TB data Disk (D Drive)

then fine.

But when a default Windows 2008 R2 installation requires 40GB, why so much?

if it's just so you can use up storage space, bad idea, save it for later.
LVL 28

Assisted Solution

bgoering earned 1000 total points
ID: 34966429
I have a M500i Promise - I would create at least two raid groups from your drives. Personally I have 15 drives with two 7 drive disk arrays and a hot spare for a lab environment. After you create your Disk Arrays, start on the logical drives. Use either RAID 5 or RAID10 for higher performance. Mine is just a lab environment so I mostly use RAID5. Now my particualr m500i isn't on the HCL (but so far has worked fine). If this is for production make sure you have a supported SAN!

Promise is a bit different in that you your "Disk Arrays" are just a group of drives - and you don't actually set the RAID level until you create logical drives - you can mix RAID10 and RAID5 on the same group of disks. As far as size my default size for vmware is 500GB LUNs - use whatever you want but make sure you don't exceed 2TB for any single LUN. In my opinion smaller and less vms per LUN is better because of LUN locking issues, but this isn't nearly the issue it used to be with say ESX 3.0.1.

Good Luck
LVL 42

Expert Comment

by:Paul Solovyovsky
ID: 34966618
I would be carefull with 2TB SATA drives.  Depending on IOPS you could run into issues down the road since the SATA drives don't have IOPS of SCSI or SAS drives and rebuilds can take forever compromising the RAID set.  I usually prefer going with less storage and better hardware.  With thin provisioning you can grow as needed.

If there are only 2 VMs you should be ok unless you're running heavy IOPS system.  If you want to leverage this for more VMs in the future I would look at SAS drives.

Author Comment

ID: 34972606
Just so you have some more details.
I have more details. I have PROMISE VessRAID 1840i and SATA 2TB 7.2K 64MB.

bgoering idea seems to fit into my problem, and it fits Promise support recommendations. Also, spare drive has been included into this configuration which is what I was planning to do.

The only problem here is I have 9 x 2TB hard drives.
Do you think running:  2x RAID 10 + 1 spare would work best in this set?
I would than create 5-7 logical drives for OSes and several DATA drives.
The remaining data will probably be used later if needed.
hanccocka you are right about OS drives of 500GB will be too big. I will save remaining space for future expansion.
paulsolov this is not highly demanding environment (in terms of resource usage), so I do not think there will be a problem with the hard drives.
I do not plan to have more than 4 VMs running on it for next 3-4 years later it can change. For now I will be running only 2 VMs.  
LVL 124
ID: 34972669
I think this is an excellent plan
LVL 28

Expert Comment

ID: 34972888
Yes - in order to minimize rebuild time create at least two raid groups of 4 drives each plus your hot spare - then create your LDs as RAID 10 for best performance.

I must caution you though that performance won't be stellar on SATA drives if you need to sustain a large number of IOPs...

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