Ibm DS3524 and raid

[inetiqa]

Hello, I have to install a DS3524 connected to an IBM server with VMWARE installedESX4.0.4Update4.
The DS3524 is connected via SAS 12 are installed 300GB HD and 2 SD of thecontroller is mounted to the cache 2GB.
I wanted to know if you should set up a RAID6 from 11HD and 1HD hotspare and if I can then create a single logical unit of 9x300 = 2.7 TB?
thanks

[inetiqa]

Hello, I have to install a DS3524 connected to an IBM server with VMWARE installedESX4.0.4Update4.
The DS3524 is connected via SAS there are 12 HD 300GB installed and 2 controller with 2GB of cache.
I wanted to know if you should set up a RAID6 from 11HD and 1HD hotspare and if I can then create a single logical unit of 9x300 = 2.7 TB?
thanks

[MauroBonder]

Hello,

No you can´t, VMware have limitation of VMFS maximum 2TB minus 512B

look

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100356...

[inetiqa]

Thank you.
But what raid configuration should I use? RAID5 or RAID6 or RAID10?
thanks

[cho9045]

KB Article: 3371739 (http://kb.vmware.com/kb/3371739

I think the above KB article could be help of you to understanding the limitation of VMFS LUN size.

I think you can create 2.7TB RAID6 volume but after that you should devide it into LUNs smaller than 2TB each. Then those LUNs (less than 2TB in size) will be presented to ESX host. Consult with storage documentation and/or support engineer on how to build RAID volume and create LUNs.

Hoefully this answers you.

[VirtuallyMikeB · Accepted solution]

Good day,

There are, of course, ways around what appear to be limitations.  You can have a 'logical unit' larger than 2 TB if you use extents.  Go ahead and create a 2 TB LUN and a 700 GB LUN.  Add the 2 TB LUN as a datastore, then increase the size of that datastore within the vSphere Client.  You should see your 700 GB LUN available.  Within the datastore properties, you should see something similar to the below screenshot.

And under Configuration > Storage, you'll see the maximum available space is larger than 2 TB, like below.

Of course, these screenshots are from a vSphere 5 environment, but for these purposes vSphere 4 and VMFS-3 will be similar.  You'll also still be constrained to the .vmdk size limit of 2 TB minus 512 B.

Let me note there are some arguments against using extents, but it doesn't sound like you'll run into such scenarios.  Check out this post for a debunking of VMFS myths, including the use of extents: http://virtualgeek.typepad.com/virtual_geek/2009/03/vmfs-best-practices-and-counter-fud.html

Cheers,

Mike

Mike

http://VirtuallyMikeBrown.com

https://twitter.com/#!/VirtuallyMikeB

http://LinkedIn.com/in/michaelbbrown

[VirtuallyMikeB]

As far as the RAID configuration, it depends on your needs.  You already mentioned keeping a hot spare, so that's good.  RAID 5 uses only one parity disk, so you'll lose 'only' 1 TB to parity - writes are decently fast but you're only protected from single disk failures.  You'll lose 2 disks and 2 TB to parity with RAID 6, but you'll be protected against a second disk failure while you replace the first failed disk.  And with RAID 10 you'll lose half of your total storage to mirroring.  You'll also need an even number of disks for RAID 10, so you'll either use 10 or 12 disks (perhaps you'll keep 2 hot spares?).  You're looking at 5 or 6 TB (likely a bit less) if you use RAID 10, but of course, you're mirroring all your data so you're pretty well protected.  These are all choices you'll have to make.  Computing is all about trade-offs.  In this case, you're trading protection for speed and usable space.

Cheers,

Mike

http://VirtuallyMikeBrown.com

https://twitter.com/#!/VirtuallyMikeB

http://LinkedIn.com/in/michaelbbrown

[inetiqa]

Thanks to all. An IBM consultant who has advised me
configure a RAID10 with 10HDD and create 2LUN each managed by a
different controller. At this point I do not know whether it is expedient to create a single
Datastore or whether to create 2 different Datastore. what
Recommended?