Large Disk Support?

[jstraten]

I am evaluating VMware ESXi to host a SAP development environment. I really like the concept and the vSphere client.

However, we ran into one big problem that would be a showstopper for us: The 8MB block size limit for VMFS3.

Basically, we would like to use a 5TB RAID array, but the 8 MB limit reduces our available disk size down to 1.5GB. I looked around for a solution, but I couldn't find one so far. Ideally, we would like to give the entire RAID to the VM.

I understand that we can use LUNs in larger environments, but we want an "all-in-one" box.

Hardware:

Adaptec 5820 RAID

6x 2TB HD

32 GB RAM

Is there an undocumented option to increase the block size to at least 16MB? Any other options?

Thanks,

Jens

[NuggetGTR]

8MB block size will allow 2TB file sizes but you can have a 2TB data store x 32 extents which is a 64TB volume which im sure will do for most people atm. I dont like using extents but if you need the space you need the space.

[AndreTheGiant]

Is there an undocumented option to increase the block size to at least 16MB?

No... and note that the 2 TB limit is related to SCSI2 standard.

When ESX will work with SCSI3, this limit can be changed.

With iSCSI storage the simplest solution is use guest iSCSI initiator and point the data LUN directly without the ESX limit.

Andre

[jstraten]

This solution sounds promising, but how do I extent my volume?

I apologise, but I am only using ESXi for about three days now and so I am still not familiar with all the options.

Is there a step-by-step instruction on how to do this?

Are there any risks involved?

[jstraten]

Thanks Andre.

I am guessing that Openfiler is such a solution, correct?

What is the better option? Using extents or using iSCSI through a guest VM?

I am still puzzled that VMware simply doesn't allow bigger block sizes. I mean what's the problem with giving some power to the user?

[AndreTheGiant]

Openfiler is a solution, but IMHO for testing purpose.

Or you have native iSCSI, or you can use guest extends.

Note that VMFS extend does not help, cause you can have a VMFS datastore greater than 2 TB, but your vmdk files will still have the 2 TB limit.

Andre

[jstraten]

Thanks Andre.

Native iSCSI would be through a second system acting as a file server, correct? We would like to stay away from that...

A guest extend is basically using a dynamic disk on windows, right?

I guess the underlying question is: Can I use the lost disk space by using an extent?

I mean right now I still haven't found a solution to even create two VMFS3 storages. Basically, ESXi only allows me to create one VMFS3 storage per physical array from what I can see so far.

[NuggetGTR]

Hahaha thats right forgot about that can make bigger volumes but the vm's disk is still limited by file size of 2TB.

yeah adding the space within the guest OS independant of esx would be the best bet, didnt think this one thew when posting, appoligies.

Yeah you could add multiple disks to the vm and make them as dynamic disks within windows(guessing you would be running 2003 min) to make one volume.

few ways to tackle it

[jstraten]

But how can I even make the rest of my volume visible to the guest OS? It seems that ESXi also has a one to one relationship between the physical volume and the VMFS3 volume.

[NuggetGTR]

I havent delt with raid volume so much with esx/i I deal with LUNS which I format as a whole vmfs3 volume, but I couldnt see why you couldnt use fdisk to create and setup the partion and vmkfstools to format it, least worth a try.

sure someone with more skills than myself can confirm

[jstraten]

In the end I found that my RAID controller (Adaptec 5805) allows me to create multiple LUNs against the same RAID array. This way I could partition my RAID array into smaller ones (<=2TB).

Please note that you still have to delete and re-create them in ESXi because ESXi once again assigns a smaller block size to them during install.

I also found that even though you can only assign 2TB to a virtual machine at build time, you can later on assign additional hard drives to increase your available disk space. Furthermore, if you are using Windows, you can merge these drives into a dynamic disk in windows.

Cheers,

Jens

[AndreTheGiant]

Native iSCSI would be through a second system acting as a file server, correct?

No... I mean enterprise storage that works with iSCSI.

A guest extend is basically using a dynamic disk on windows, right?

Right

Andre