I’ve been hearing from a lot of people that the VNX will eventually be similar to the VNXe. I didn’t believe EMC would do that until they came out with the VNXe 3200, but now it is looking like it is a possibility. I’ll need to provide a quick recap of the history of the VNXe and VNX to give you an understanding of why I believe the two are converging into a single platform.
VNX and VNXe History
For the last few years EMC’s marketing strategy has been selling the concept of a Unified VNX. The rest of us know better—the GUI is unified, but the array really isn’t. Prior to the VNX there were the NS120/480/960: CLARiiON and Celerra models that were “unified”; however, when they were first released, the GUI wasn’t even unified. Later, you could upgrade to a higher DART and FLARE code and you would get Unisphere, which then unified the GUIs (the hardware was still separate, though).
Instead of getting a unified array, you could also buy either a block-only or file-only VNX/CX. For a block-only array, Storage Processors serve data via iSCSI/FC/FCoE. On the file side, you have Data Movers that serve data via CIFS/NFS/iSCSI (VNX iSCSI via Data Movers requires an RPQ from EMC to support it, and is also hidden from the GUI).
Why is this important to know the history? Because on all VNXe models, prior to the VNXe 3200 release, iSCSI was done via the file/Celerra side. Now why is that important? Because it was and is terrible.
Breaking It Down
Here is a breakdown of some of the challenges with previous VNXe models prior to the new release:
- First of all, to create an iSCSI LUN on the file side, you would need to first create your RAID Groups and LUNs, then present the LUNs to the file side. Those LUNs would be marked as disk volumes on the on the file side and put into a file storage pool. After that, you would create a file system which would stripe or concatenate volumes based on the file AVM (Automatic Volume Management) algorithm. After that, you would then create your iSCSI LUN from the file system space. Long story short: there are a lot of layers and it’s the best for performance.
- When replicating iSCSI LUNs via the file side, you would need an additional 150% of the LUN size free on the file system on each side, source and target. To put it in perspective, if you had a 100GB iSCSI LUN, you would need a 250GB file system size on each side—which creates a lot of overhead. (Much less overhead using thin provisioning, but that slows things down.)
- iSCSI LUNs are limited to 2TB in size on the file side.
- Your only option for replication is either host-based or Replicator V2, no RecoverPoint, MirrorView, SAN Copy, etc. as is on the block side. (You can replicate your entire VNX file with RecoverPoint, but that is a terrible configuration.)
- For those reasons and more, I have lacked confidence in the VNXe since the beginning and cringed when having to fix them, since it always seemed there was either a replication or network problem.
So why is the VNXe 3200 different? Well, it is different enough that I think it should have been announced as the VNXe 2, or VNXe with MCx, or in some big way like the VNX 2/VNX with MCx was announced.
There are some major differences with the VNXe 3200 and previous models.
- Fibre Channel ports are now available
- Better use of EFDs
- FAST Cache can be used
- Tiered pools can be used
- iSCSI now appears to be block based
Note: My only evidence of 3. is that when you put an iSCSI IP address on an Ethernet adapter, you can no longer use LACP on that port. This would make sense, since there is no LACP on the block side for iSCSI, only on the file side. Also, with the addition of FC ports being available (they’ve obviously been allowed access to the block side of the VNXe 3200), so that means block iSCSI would be possible too.
So if I’m right about the iSCSI, that means a few things:
- iSCSI replication between pre-VNXe 3200 and VNXe 3200 models won’t be compatible (I asked some EMC product managers and was given a response that they can’t comment).
- iSCSI LUNs should be able to be replicated between a VNX and VNXe (depending on if they put MirrorView into the VNXe and at the very least you should be able to run a SAN Copy pull session to migrate it off a VNXe onto a VNX though)
- iSCSI LUNs might be able to be used with RecoverPoint (depending on if the VNXe has a RP splitter, but they might allow host based splitting with a VNXe and iSCSI if no splitter is embedded)
It looks like EMC is taking the VNXe in the right direction, but there are still some unknowns. Until then, it seems like a decent Unified Storage Array if you need shared storage and either didn’t want to replicate your data or you were using host-based replication. I’m hoping that if EMC chooses to do this same hardware unification with the VNX line, they get everything figured out with the VNXe first—appears they’re making the steps to do so.