VDev/Zpool configuration guidance

[rmccullough]

I am setting up a new FreeNAS server and am looking for some guidance. I see a lot of recommendations about using raidz2 or raidz3 depending on the number of disks you have, but 1 thing that is not clear is if "hot spare" drives are counted in that.

My server has 9 x 2TB disks. I will also be backing up to a cloud service which I purchased an "unlimited" plan with.

I was thinking that 8 drives should be in-use with the 9th drive being a hot spare. If that is true, am I better off creating a mirrored (2 x 4 disk) VDev? Or is raidz2 a better option? Should I even be considering raidz3?

It looks like I could also configure 8 or 9 disks in a raidz2, which would give me 12TB or 14TB of storage with a reasonable amount of failure protection. Perhaps that is a better option since a mirrored configuration would only give me 8TB of space?

 

[MatthewSteinhoff]

I wouldn't bother with a hot spare. Either keep it on the shelf or add it to the pool. But having it running up hours and sucking down electricity while performing no purpose seems wasteful.

I wouldn't bother with RAIDZ3 unless your FreeNAS server is inaccessible for LONG periods of time. The likelihood of a multiple drives failing at the same time before a replacement drive is installed is low. RAIDZ2 is plenty to let me sleep at night.

RAIDZ2 is space efficient. Mirrors are tops for performance but give up a lot of space for data protection.

If you're just looking for solid, safe storage, throw all the drives in a RAIDZ2 pool.

Cheers,
Matt

 

[RickH]

You didn't mention what you would be using the FreeNAS server for, but the type of data and access specifications can play a big role in how you set your drives up...

If your server is going to be used for media storage, local backups, or some other type of storage were redundancy takes priority over performance, throwing all of your drives in a RAIDZ2 pool is your easiest and best option.

If you're going to be doing something that's more performance oriented (VM's for example), I would suggest configuring your drives in 3 - 3 drive RAIDZ vDevs - this would give you a raw usable capacity of 12TB (less when you factor in the 80% rule) and provide much better performance. The downside to this approach is that each vDev will only survive a single disk failure (in theory you could loose a max of 3 disks at once as long as it was one disk from each vDev). If you every found yourself in a scenario where you had 2 drives from the same vDev fail, you would have to recover your data from your backup provider...

I would second the option that a 'hot-spare' is a waste of resources - just make sure that you configure your SMTP server and alerts correctly and you'll know about any pending drive failures long before another drive goes out.

 

[rmccullough]

Good catch @RickH. Yes, it will primarily be a media storage and backup server. I may add VirtualBox, but it would be very light usage.