iSCSI from guest or mounted VMFS?

[jasonsfa98]

I am stuck. I am about ready to do a few P-to-V conversions but before I do I want to make sure I setup my storage correctly. Any help would be GREATLY appreciated.

Setup

Dell R710 running ESXi 4

Dell EqualLogic PS6000 iSCSI SAN

Currently, I have a couple very large volumes on the SAN (1.5 - 2.0TB) to be my datastores mounted to a couple Suse Linux ES guest. I have separate volumes/datastores for the OS itself as I mount the large volumes/datastores in file sharing areas /home, etc. Although the 1.5 - 2.0TB should last us quite a while, I fear that I may have to increase the storage space in the next 2 years. From what I have read, I cannot just increase the volume size on the SAN and then increase the VMFS datastore. If this is true, that may put me in a tough position later on.

So my question is- would I be better off using an iSCSI initiator from within the guest to mount those large volumes directly from the SAN? Would I gain the ability to resize those volumes in the future?

I am losing sleep over this...

Thanks,

Jason

[binoche]

1, ESXi 4 can not support single lun more than 2TB-512B; this limitation may be removed in the future releases

2, but VMFS can support add more luns as extents, for example 1.5TB1.5TB1.5TB, now VMFS total 4.5TB

3, VMFS can support to add more extents on the fly

4, ESXi 4 can support EqualLogic iSCSI SAN well, such as multipathing, multi iSCSI sessions, portbinding; my guess it will be good idead to move iSCSI from guest OS to ESXi,

binoche, VMware VCP, Cisco CCNA

[jasonsfa98]

So I assume iSCSI LUNs can be used as extents drives?

If so, that solves one problem, but then I need to figure out how to increase the size of the disk that my guest sees. I suppose this could be handled within Linux with LVM, but I am not sure.

Thanks for the tip.

Jason

[VMmatty · Accepted solution]

I think the answer will almost always come down to "it depends" rather than a "this is how you should do it." Will you need to perform EqualLogic snapshots or replication on that large LUN? If so, it might make more sense to have it as an iSCSI attached volume inside the guest rather than a large VMDK file on VMFS storage. You'll still be able to expand the LUN on the fly if you need to. That way the snapshot could potentially be application aware, though I'm not sure if the EqualLogic Host Integration Toolkit supports Linux (maybe, not sure).

If you do attach to volumes inside the guest rather than VMFS then you'll need to do any multipathing inside the guest rather than at the ESX level. Not better/worse, just different.

Make sure you understand all of your requirements before making any design decisions that will be hard to change in the future.