We only need a about 2 to 3 TB of storage for the virtual servers after RAID (ideally RAID 5).
Has anybody used the QNAP TS-509 Pro it can be used as a iSCSI target server, it also has dual gigabit NICs. Ive seen some very good reviews about this NAS. Any ideas? or is a custom Openfiler SAN better.
As for Openfiler anyone running it on a HP ProLiant DL180 G5.
1) Disk Drives - moving at 10k rpm on some ball bearings these are most likeley to fail. So hot swap is a must, and use enterprise level SAS drives rather than budget SATA drives if you want the highest disk reliability.
2) FANs - again spinning at a few thousand RPM on ball bearings, these can fail, make sure they are hot swappable and more importantly, make sure the case design is clever enough for you to be able to hotswap them in situ, in the rack cabinet.
3) O/S. Can become corrupt. If your SANs OS goes down then so does your SAN.
4) Electronics - the storage controller and network card come under here - both items which could take your entire SAN down - BUT microprocessor devices with no moving parts are ultra reliable and I wouldnt expect a controller or NIC to fail within a 5 year lifespan, it is extremely rare. Can be offset by multiple NICs and multiple controllers if your totally paranoid.
I would come at it from this angle:
1. Ideally for maximum disaster proofing / recovery you want to have 2 mirrored SANs spread apart in different buildings. This is the ideal scenario as if one san dies you have the other one which you can connect to.
2. A SAN is a dedicated storage device, with battery back up cache and possibly solid state cache drives. As such it should theoretically be far more reliable than just a normal windows box shoved full of disks. You should run in Raid 6 with a hot swap drive so that your SAN can sustain two concurrent drive faliures, and you should make sure the SAN has good same business day warranty on it, and that it is set up to alert you the minute it notices something going wrong.
3. If your consolidating from local storage on many older servers to shared storage on a new SAN then really you are giving yourself a big upgrade in relaibility - I'd trust a Sun 7110 over all of the old servers with old SATA / SCSI hard drives we had.
We could not afford a SAN and a virtualisation solution in a single fiscal year.
We decided to virtualise first after coming accross Promox VE. We have created a cluster of machines where we can migrate machines within the cluster. Moodle even migrates in real time Also allows for easy backups etc.
It gives far more functionality the ESXi and was we also felt it was better then Xensource and Xen open source.
Proxmox VE adds a great front end to openVZ and KVM that can virtualise both Windows and Linux machines.
We will add a SAN (openfiler) solution to this next year, but I would see the SAN as single point of failure unless it was mirrored. We have got a resilient solution spread accross 3 servers in a single cluster.
Given that many of servers are now virtualised has given us greater resillience and flexibility for the management of our infrastructure. A SAN would enable us to provide greater IO and run more VMs per server. If we lost the SAN then we would lose all VMs! So I think I will still balance the server load between local and SAN storage.
We also saved a reasonable amount of money not using the extended commercial versions of Xen and VMware.
I do not think there is a right or wrong answer for whether to use a SAN with VMs. Depends on your own server loadings and IO requirements as to which solution will work best for you.
Last edited by monkeyx; 22nd June 2009 at 06:00 PM.
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