SAN or JBOD to house virtual machines?

[Ed_Flecko]

Hi eveyone,

I need a reccomendation.

We have a small network that I'm planning on virtualizing using ESXi 5.0. The existing servers are all Dell, and they're anywhere from 5-8 years old, 32 bit servers (2550, 2650 and 2850 type).

I'm planning on buying a new, probably 1U server that will run ESXi, and another JBOD type server (like those from IX Systems, whci are really just SuperMicro servers with IX System logos) that will run FreeNAS and a bunch of disks that will be home for my existing servers - I'll either P2V them or perhaps build them from scratch.

My question is: a JBOD will work just fine, won't it? I'm a little confused on the difference between the JBOD and a true SAN, but I'm thinking a JBOD (which will run FreeNAS, or will a JBOD run any OS at all???) will work just fine, won't it? I'm thinking that whatever I end up using as the "home" for my virtual servers should have FreeNAS and ZFS for fault tolerance and expandability should I need more file share space, etc.

Does anyone have any experience along this line of what I'm thinking of doing? Any comments, recommendations, , performance caveats, potential pitfalls, etc. would be appreciated.

Thank you!

[mcowger]

A JBOD is Just a Bunch of Disks.  No intelligence.  By putting FreeNAS on there you make that JBOD into an array (not a SAN - a SAN is the storage network itself - common misapplication of terms) by adding the intelligence that FreeNAS brings (things like RAID, etc).

[Ed_Flecko]

Thanks Matt!

O.K., so an "array" (JBOD with FreeNAS) has similar functionality in that they both have disaster recovery capabilities, right? The "array" would have FreeNAS (and the underlying ZFS intelligence) and the SAN would have something like RAID 5, 6, 10, etc.?

Is that a fairly accurate description?

From a performance perspective, would there be any pros/cons of going one way versus another? I would *think* on a small scale like I'm describing, there probably wouldn't be much, if any, noticible performance difference to the end users.

What do you think?

Ed

[mcowger]

I think you are missing the terminology a bit.

A JBOD is an enclosure with some disks.  Nothing more.

An array adds some sort of intelligence onto the JBOD, making it capable of doing things like expose those disks to more than 1 host, add fault tolerance (like various forms of RAID, including what ZFS brings to the table) and higher level stuff (like disaster recovery and remote replication, etc).

A SAN is simply the network that connects your array to your hosts.  It standard for Storage Area Network.  It is most definitly NOT the array or JBOD.  Its the collection of switches and cables that connect the array to hosts.  If you connect your hosts directly to the array (which is possibly, and even common in smaller shops), you dont even HAVE a SAN.  Now, many people (esp. on this forum) use the term 'array' and 'SAN' interchangeably, but this is not correct.

As far as performance....its highly dependent on workload.  But for your use case, you basically HAVE to put FreeNAS (or similar) in front of your JBOD, because you need to connect the storage space to multiple hosts.  To do that (in most cases) you need the intelligence that the FreeNAS (array) layer brings.  The FreeNAS layer can impede performance (its a layer between your apps and the disks) but it can also improve performance (by adding additional caching, etc).

[Ed_Flecko]

Thank you Matt.
*If* I understand you correctly, when you refer to SAN (I'm trying to be 100% accurate here), you're referring to the "fabric layer"? I have the "Dummies" guide to SANs, I'm trying to completely understand you.

:-)

Also, the way *I* see it, I could either...

1.) Buy a server with a bunch of disks (so I have room for future growth, eitther by installing more virtual servers, etc.), install ESXi and then start installing (or P2V converting my existing infrastructure) my virtual servers. In this case, my fault tolerance would be dependent upon the underlying hardware RAID functionality...OR

2.) Buy two servers - one to host ESXi and the second would have a bunch of disks and I'll run FreeNAS and will be my iSCSI targets for my soon to be virtual machines. In this case, I'm relying upon ZFS for my fault tolerance.

Does this sould correct?

Ed

[mcowger]

Yes - the SAN is the fabric itself.

Either of your options are reasonable.

Option 1 is cheaper in the short run, because you only buy and run 1 server.  Its also more supported (assuming you buy supported hardware) because FreeNAS is not an officially supported storage system (although it works fine).

Option 2 is more expensive in the short run, and technically unsupported, but it does give you more options in the future.  You have more options for replication to another site, more options for backups and, if you wanted to add another host in the future for hosting more VMs or for redudancy, you could do it (which you couldn't do with Option 1).

[Ed_Flecko]

Excellent...thank you Matt.

If I understand things correctly, it's my "host" server (in my Option 2 scenario, it's the server that has ESXi installed) that is the server which needs to offer the better performance, correct? From what I'm told, I guess from an iSCSI target perspective, the server that actually is home to the virtual machines doesn't need to be a real performance server.

For a small environment like mine, I've been told that the Intel Xeon "Westmere" series quad-core processors offer good performance at a good price. I'm thinking if I built my host server using 1 or 2 of these processors and a decent amount of RAM (at least 16Gb), this would probely run rings around my existing, old servers. I'll buy something like an IXSystems 2U running FreeNAS for storage.

Comments? Suggestions?

Thank you,

Ed

[mikeyb79]

How about a virtual storage appliance that will allow you to scale beyond a single host in the future?

[SantiniStorMagi]

Hey Mikey

Looking at your discussion, you may want to have a look and possibly evaluate StorMagic's SvSAN.

So far ticks all the boxes around your requirements, take a look at this comparison we did on VMwares VSA ( slight out of date, but gives a good idea on functionality).: http://www.stormagic.com/svsan_vmware_vsa_comparison.php

Cost effective, Very flexibly, easy to use (vcenter integrated) and scalable.