Failover in the event of a disk controller or NIC failure

[jthompson]

I am looking to setup a small SAN for the company I work for. I’m pretty new to the whole SAN concept, but, I’ve been doing a lot of reading.

Briefly, my needs would be:
-Around 2 TB of fast disk storage (probably SAS disks)
-At least double that for backup, etc. (SATA disks)
-To use 10GbE iSCSI targets
-A way to create slower simple storage for Macs and Windows Clients

It seems from what I’ve read so far about FreeNAS is that I can do the following:

-Build a box with one disk controller, one 10GbE NIC, add my disks, create some RAID z2 pools and serve them up over 10GbE iSCSI, CIFS, AFP, etc.

My concern is that if I start putting 8 or more servers on this box, how do I handle a disk controller or NIC failure.

My question is:
Does FreeNAS support automatic failover if one disk controller fails or if one NIC fails?

IF the answer is yes… Then, what kind of crazy hardware would I use to achieve such grandiose reliability?

Maybe something like?
http://www.supermicro.com/products/system/3U/6036/SYS-6036ST-6LR.cfm

I’m not looking for something for nothing…
And I realize that since its commercial, I may end up paying for something like NexantaStor.

I just like to use open source (and buy support when needed) and support the community because I believe *nix, bsd, gets the job done.

Any answers are appreciated.

 

[Al562]

Hi Jthompson,

Does FreeNAS support automatic failover if one disk controller fails or if one NIC fails?

To the best of my knowledge FreeNAS does not currently support this type of redundancy. If I am mistaken I'm sure someone better informed will correct me.

Regards,
Al

 

[matthewowen01]

redundant NIC is easy and supported, look under the Link Aggregation section. there is an option for failover but as i recall when i setup mine, there was another one (you'll need to read up on all the options it escapes me) that will utilize both at the same time and if one fails it will keep working.

redundant disk controller is not a function of any setup, it's all about how you build your system. you just have to make sure no controller has any more disks than your pool can survive loosing. ie, if you have a raidz2, each controller can have no more than 2 disks.

 

[jthompson]

So in RAID z3, each controller could have no more than 3 disks?

Hmm... that means you would be limited by the number of PCI express slots, too I presume.

What about ZFS mirroring? Could you do it different with mirroring?

 

[matthewowen01]

So in RAID z3, each controller could have no more than 3 disks?

Hmm... that means you would be limited by the number of PCI express slots, too I presume.

What about ZFS mirroring? Could you do it different with mirroring?

raiz3 is not supported by the version of zfs that FreeNAS uses but yes.

mirroring would be the same. 2 controllers, each with one side of the mirror.

 

[Al562]

Hi Jthompson,

you would be limited by the number of PCI express slots, too I presume.

Yes. The required number starts to climb as you add redundant controllers and NIC cards.

Could you do it different with mirroring?

Sure, if you had 2 8 port cards you could create 8 RAID1 arrays, or 2 RAID5 arrays lets say. If one of the controllers dies the individual arrays would continue to run.

The thing to remember about redundancy and automatic failover is that often it's a devils' bargain. In the event of a controller or NIC failure in the type of server we are postulating here, you'd have to replace the failed component ASAP. That means having spare parts on hand (unless you are willing to pay through the nose for overnight shipping or your clients can accept reduced network performance for a while) and bringing the server down for maintenance. In terms of overall cost and client happiness you are often better off having 2 cheap servers than one really expensive one.

Regards,
Al