DAS or NAS for VMware?

Question

I am going to be implmenting a VMware vSphere 4 setup in our company. At first I had the plans of using a Netgear ReadyNAS business applicance for VM storage via iSCSI. But as I was looking around for parts for my VMware server (license 2/3) I was thinking of a different approach.

I was thinking what if I just loaded 6 WD Scorpio Black 500GB SATA drives into the server and ran a DAS setup rather than investing in a NAS.

The reason I was thinking we need more space than anything. We are most likely never going go beyond 1 VMware server because we are so small (my server does not count) We only will be running 4 VMs max. Also we do not have licenses for the VMware HA components.

What would be downsides to have the storage with the VM server in small setup like this?

Any advantages?

Backups would be handled by the vCenter server which is a separate server. So getting to the storage in either regard is not a problem.

Answer 1

I ran a VMWare attached to a NFS shared storage in a ReadyNas 1100 and the result was awful. The ESXi had to reconnect several times a day to the storage (I have to say it was all in the same LAN as the rest of the workers computers). Also, the write latency was awful (50-60ms, even 100ms with load in the server).

I tried with a FreeNAS mounted in an old server with a couple of disks (also some disks that were unused in a shelf, zero invest) in RAID-1 in a separate LAN connected via iSCSI and I have to say it's perfect. The FreeNAS server has required none attention in 3 months, and even it's not a heavy loaded server, the speed of the reading/writing is similar to a DAS, or even better than a normal (not enterprise-class) disk.

Answer 2

What you propose is perfectly fine. NAS is double the cost for half the performance (my gross simplification of our evaluation). You could even build your own NAS with a Linux box and some open source software.

Ultimately though, for 4 VMs on a single processor virtual setup, you are golden with what you proposed - we ran such a setup for a long time with no issues and it is definintely cheaper and easier to manage.

Answer 3

If you do not plan any HA features, then iSCSI NAS isn't going to buy you a lot. About the only scenario would be failure of the server, when you could re-install the server and just re-connect the datastores on the NAS. OTOH it gives you one new failure mode, where NAS box fails and you have to restore the data somewhere.

I assume the disks will be connected to some HW RAID card? Otherwise a single HDD failure will take out your datastore, which is bad. Locally attached disks chould give you better performance than NAS, especially in response times.

I have another question: if you do not plan to grow beyond single VMware server, then maybe you could take a look at the free VMware hypervisor? Or just buy support for ESXi? If your VMs do not exceed limitations of the free license (RAM and CPUs of the host), then maybe you don't really need vCenter?