New to FreeNas

[Joe Patane]

Hello all,

I've just joined and I'm planning is setting up my first FreeNAS box.

I have various Capacity Hard Drives, about 10 in total, below are the biggest of the drives I have others are 320GB & 250GB, all these drives at the moment are in external enclosures:

2 x 3TB, 2 x 1TB, 2 x 500GB.

I'm planning of getting another 3TB drive.

My problem is that 1 of the 3TB, 1TBs and 500gb drives etc. which are in the external enclosures, have all data on them and are full to the rim!!

I want to include the biggest ones in my freeNAS build, so what's the best way to setup freeNAS using the 2 new unused 3TB drives I will have and the ones with data on them, I'd like redundancy as most of the data on these drives is old and not easy to come by if the drives fail, hence this project.

Any advice appreciated.

Thanks

Joe

 

[Cupcake]

Well if you want redundancy you should probably go with Z2. This needs 4 disks at minimum and would in your case be inefficient, since you don't have enough big drives (only the space of the smallest drive in a vdev would be used). Meaning, if you use the 2x3TB and 2x1TB drives in a RaidZ2, you would effectively have 2x1TB as total capacity of that pool. Pretty wasted huh?

If you really insist on getting the maximum of space and redundancy with the drives you have, you would probably need to create three vdevs, each mirrored with only 2 disks of the same size. You can not include drives with existing data, so you would have to wipe them. You can do this by first creating a zpool with only one vdev, the one with 2x3 TB. Then empty your full external drives by copying everything to the NAS. After you've done that you could add the now empty drives as a second and third vdev to the existing pool.

Word of warning though: If you really create a pool with 3 vdevs, know that if ONE of them fails your WHOLE POOL is gone. The moment you add another vdev to the pool you can no longer remove it! Just think carefully if it's worth the hassle, risk and reduced redundancy of the way I've described. Maybe someone else will come up with a better solution. I would save money and do it right from the start. Get two or four more 3TB drives, make one big RaidZ2 with the four/six drives and be happy.

 

[Joe Patane]

Hi thanks for the reply.

So if I start with 4 x 3TB drives, when I move all the data from the other 3TB drive can this be added to the existing volume and extend it's size? or do I need to do in pairs for the Raidz2, bring the total number of drives to 6x3TB, which would give me an additional 3TB usable. I guess what I'm trying to get to... is it easy to extend the size of the existing RaidZ2 volume without losing data?

Thanks Again,

Joe

 

[Cupcake]

Hm I'm confused, you said your 3TB drives are ununsed, so why would you need another 4x3TB? Doesn't matter, I think I can answer anyway.

First you should click through this presentation: http://forums.freenas.org/threads/slideshow-explaining-vdev-zpool-zil-and-l2arc-for-noobs.7775/
It really helped me understand the whole pool/vdev thing.

Yes it is quite simple. Your pool can consist of any amount of vdevs (vritual devices). Whenever you add a vdev to your pool, it's total size automatically increases. Also, freenas stores data on that vdev as well from this point on, so you can't remove it anymore. So if you want to extend your pool, simply add another vdev.

Now for the RaidZ2. RaidZ2 works on a vdev level, meaning that your virtual device consists of some drives in RaidZ2 mode and all together forms one vdev. So basically you could have a pool with three vdevs: vdev 1 with a four disk RaidZ2, vdev2 with two mirrored disks and vdev3 in JBOD mode. Your pool will use all of them evenly to store data. The problem is, that your whole pool is only as safe as the "weakest" vdev. If you have five RaidZ3 vdevs and a sixth vdev without redundancy, if that sixth vdev fails your complete pool is gone. Hence it's recommended to add vdevs with the same type as the ones you already have in use (there are probably some other reasons as well regarding freebsd internal stuff, I dont know). This way all vdevs have the same chance of failing since they have the same redundancy.

Finally let me make one comment since I've built my first freenas this christmas and fell into a trap: I started off with 3x4TB in RaidZ1 and thought that after some time, I can add another 3x4TB RaidZ1 so that I have 16TB in total with six drives. Now let's see what a RaidZ2with the same six drives minus two parity drives would give us: (6-2)*4TB = 16TB. So, I have exactly the same amount of storage, but the big RaidZ2 is a lot more redundant than the two RaidZ1 vdevs.

In your case you want to start with a 4x3TB RaidZ2, giving you two usable disks and two for redundancy (total 6TB). After some time you may want to add another 4x3TB in RaidZ2. Now you have 12TB with 8 drives in total. Let's see how much storage a 6x3TB RaidZ2 offers: (6-2)*3TB = 12TB. So same space. In this scenario you at least have RaidZ2 redundancy over all vdevs, but you'r "wasting" two drives so to speak. Reason is that RaidZ1/Z2/Z3 always use 1, 2 or 3 drives for redundancy, no matter how big your vdev is. This means that a bigger vdev will bring you more TB / $$$. But you have to initially spend more $$$.

I hope this long post helps you some how. If not, really go check that link I've posted at the beginning. You absolutely need to know how vdevs and pools work. What you can't do is extend a 4x3TB vdev to a 6x3TB vdev. You can not add drives to a vdev, you can only add more vdevs to the pool.

 

[Joe Patane]

Hi thanks for that.

Sorry for the confusion, was just thinking of taking your recommendation and going out to buy a further 3 3TB drives and with the one I already bought and start with a 4 drive setup from get go.

Will look at that link you sent.

Thanks again