Best way to setup 3TB of storage for a file server?

[Wasisnt]

We were told that our new IBM DS3512 cannot be setup like our current NetApps as a file sharing device so it looks like we will have to make a file server VM and set it up as a file server. Unless this information is wrong but I cant seem to find out otherwise.

So I have 2 LUNs that that total 3+ TB. One is 1.9 TB and the other is 1.3 TB. I notice if I make an extent out of them I can get the 3TB in one datastore but the file size wont allow me to use all of it even if I use the 8MB block size. I dont even know if this is a bad way to do this or not.

I read in another post about using RDM to set this up but I dont know how to go about doing that on the storage or in VMware. Is this the way to go and can anyone give me some pointers?

[Mauro Bonder]

If you need more than 2TB disks you can really use RDM, is even more appropriate when you have great access to I / O. If you prefer to use VMDK, it is limited to 2TB - 512Minus, being with 8MB blocksize.

I advise you to use RDM. With RDM you mapped to the VMware host, but does not add the Configration> Storage. You add directly to the virtual machine

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1031041

[Wasisnt]

Should I use physical or virtual for compatabilty mode? If I use virtual and use snapshots wont they be huge if I have 2-3TB of data on the drive? Or are you saying if I use virtual it will still be limited to 2 TB? And would using physical affect things like vmotion for the VM etc?

[Wasisnt]

The only way it seemed to work is if I had my 3TB as 2 LUNS and then added the RDM as 2 drives to the VM and then made a spanned volume within Windows. When I tried a 3 TB RDM it said something like it was too big to store with the VM.

[Mauro Bonder]

Although the LUN size is limited to 2TB - 512 bytes, the VMFS and  datastore volume size limit is much greater. The maximum volume size is  64TB - 16KB. This can be accomplished by leveraging the maximum extents  (32) per volume.

If you require a single datastore that is larger than 2TB - 512 bytes  in size, you may want to add extents so that the datastore resides on  multiple LUNs of 2 TB - 512 bytes or less.

You really need 1 volume with 2TB + ? You cant create two volumes of ~2TB, multiextend may not is a best solutions, but if you need it. Go ahead.

[Wasisnt]

If I make an extent and use 2 LUNs to create a 3TB datastore then I cant use RDM because it only lists unused LUNs that are available with no datastores as available storage to use.

If I make a 3TB LUN on the SAN and try to attach it to the VM as a RDM using either the physical or virtual option then it says the vmdk is larger than the maximum size supported by the datastore. I though it was just supposed to link it to the VMs datastore, not put it in there?

Im wondering if I should just make 2 LUNs and then make 2 datastores out of them and then make one volume from those within Windows and call it a day.

[kwizi66]

You might try decreasing the size of the 2tb LUN. Make it an even split. 1.5tb+1.5tb.

Looks like you're experiencing something like this: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=3371739

[DSTAVERT]

Individual VMDKs need to be less than 2TB. Consider using Windows DFS to "glue" your file system back together rather than using extents or Dynamic Disks. You can also use mounts within Windows to assemble several disks into a single file system. ESXi 5 does have the ability to create very large VMFS datastores although the individual VMDKs are still limited to 2GB-512b

[Wasisnt]

Yeah I figure I will just make 2 datastores out of the 3TB of space and then attach them to the VM and make an extended volume within the Windows VM.

So would there be any advantage for me to use RDM instead of datastores for file serving?

[Wasisnt]

I just made 2 datastores out of my 2 LUNs. Then I made 2 virtual disks using the full capacity of each datastore to attach to my file server VM. Now I get alarms saying datastore usage on disk is over the threshold because I used the whole capacity of the datastore for the virtual disk. I just cant win!

Should I just stick with RDMs? How will that affect backups using VDR? I dont want to backup the secondary drive anyway because of its size. We will use our current backup solution for that.

[DSTAVERT]

You need space on the VMFS datastores for snapshots, logs and swap space. I would reduce the size of the VMDKs. You can change the destination for some of the files but that can be troublesome as well. You do run the risk of running out of space.

[DSTAVERT]

http://kb.vmware.com/kb/1002929

http://kb.vmware.com/kb/1004082

[Wasisnt]

How much space should I leave free on the datastore percentage wise?

And how about just using the RDM and what about any side affects of doing so? And if I did would I want to use physical or virtual compatibility?

[DSTAVERT]

Wasisnt wrote:

How much space should I leave free on the datastore percentage wise?

And how about just using the RDM and what about any side affects of doing so?

The best answer available here is "It depends". You would need to allow swap space equal to RAM allocated to the VM, a couple of GB for log files, space for snapshots based on how much data change there could be in a given amount of time and some margin of error for snapshots. It could leave you very vulnerable if snapshots lingered for any reason. Running out of disk space is often catastrophic.

RDM might be a good choice in your situation. There are lots of discussions on the differences and reasons for choosing virtual or physical RDM. If you have SAN based tools for backup, physical might be a better choice otherwise victual probably satisfies most situations.