Tag Archives: VSAN

VSAN – A Closer Look

VMware announced VSAN yesterday at VMworld 2013 and this is exactly the kind of thing that is going to help businesses who are looking to replace or upgrade their storage with something a little more up to date. We are just that kind of business. Currently we’re running a Fujitsu DX90 S1 with absolutely no advanced features available whatsoever.

To give you some idea of how archaic this thing is I recently had to re-provision datastores after it was decided that the current mixture of datastore sizes just wasn’t cutting it. We had a mixture of 800GB, 1.2 and 1.6TB with RAID 5 and 1+0 storage and the goal was to increase these to RAID 6 2TB. The block sizes weren’t that much of a problem since 5.x doesn’t care what size they are but I had upgraded us from 4.x to 5.1 since starting work here and best practice is to blow the storage away and re-provision.

All in all the entire project took 10 days to complete if you factor in disruption and troubleshooting.

Now, it could be argued that we have suitable storage. Our VMs have somewhere to sit and it’s all shared across the hosts and everything can see everything else. But we have no features and maintenance is taking days rather than hours or minutes. We’re currently in the market for a new SAN and we’ve been shown demos from EMC, IBM and NetApp. The storage provisioning, DR and VMware integration is light years ahead of what we have (or not as the case may be) and obviously we’re going to be walking away from these things very impressed.

However, the one thing we’re not impressed with is the price. We’ve been quoted something around £60k for the VNX5300 and over £150k for the FS2240. The IBM came in around £40k.

This is where VSAN can swoop in and save the day. We’re in the middle of a tech refresh and we’re replacing our Sun servers (don’t ask) with Dell R710 and 720 rack mounted servers and we’ve bought these things with minimal disk configurations, 2 drives for the hypervisor. What VSAN means to us is we can now fill those servers up with SSDs and HDDs for a fraction of the price of one of those other SAN vendors.

So, VSAN is essentially pooled DAS or a single shared datastore presented to hosts that are part of a VSAN enabled cluster. This is nothing out of the normal scope of what you’ll probably have running anyway. You’ll already have a host cluster if you’re using HA and DRS and you might well have a datastore cluster if you’re using SDRS.

VSAN also does away with RAID and instead employs something called RAIN – Redundant Array of Independent Nodes (a node being a host). Redundancy and protection requires 3 hosts in the cluster and VM protection comes by way of replicas where the data is written to multiple nodes in the VSAN cluster. Protection was one of the questions I asked myself when I first read the announcement and Duncan Epping (as ever) has a plain English explanation and a high level illustration over on Yellow Bricks.

As for the the disk configuration you’ll need at least one SSD per server for write-through cache and this SSD does not contribute to the overall capacity – which isn’t much of a show stopper if you’ve got a 24 bay R720XD only utilizing 2 disks for the hypervisor install. And much like tiering, data is written to the SSD first then sent on to the HDDs. Reads from the VSAN are read via the the SSD, or from the HDD if the data isn’t available on the SSD.

This is pretty much a no brainer for us. Instead of throwing in excess of £60K on a physical SAN we can now instead buy a bunch of 900GB 15k drives and combine them into a VSAN. A tenth of the price at best.

And you’ll be even more impressed by the fact that VSAN is baked into vSphere 5.5 – no appliance required.

Happy Days.

The public beta is coming soon and sign ups are open here: http://www.vmware.com/vsan-beta-register and more info regarding VSAN can be found here: http://www.vmware.com/products/virtual-san/