Expandability and adding drives. Super confused. Advice before install please?

[markhsa]

I have read quite a bit, but getting confused.

I am doing a fresh install of FreeNAS. 3 2TB disks. HW is 8 gig RAM and i3 3.1ghz.
I HAVE to be able to grow this storage though, so how is this done?

I need RAID 5 for data protection, and have read that ZFS is very good for a number of reasons.
Though, I understand that ZFS is NOT growable. Should I not use it and just use standard RAID5?

Scenario. Install with the 3 2TB drives and ZFS = 4TB of storage. Then I add a fourth 2TB drive. I understand it cannot be added to the original 3 disk set, but can be added as another device to grow it. Then I get to 6TB with 4 drives correct? Do I still have the same data protection if I lose that new single drive?

What I need is to be able to add drives from time to time and grow my storage, while still retaining the protection of drive failure.

Recomendations?

 

[survive]

Hi markhsa,

There are 2 ways to expand an existing zfs pool. You can increase the size of the old drives (eg swap 2TB drives for 3TB) and resliver (rebuild) after each drive swap & the extra space will become available when the last drive is rebuilt or you can add another "virtual device" to the existing pool. A "virtual device" (vdev) is what you actually make when you create a pool and the filesystem actually goes on top of that. In your example above your 3 2TB drives make up the vdev. To expand, ideally you would make a second vdev out of 3 more 2TB drives, add it to the first vdev and double your space (and potentially your performance).

You can add a single drive to an existing pool, but the resulting vdev wouldn't have any parity so if it failed it would take down your whole pool, in other words you *can't* add single drives to grow your pool and retain any data protection.

-Will

 

[ProtoSD]

Scenario. Install with the 3 2TB drives and ZFS = 4TB of storage. Then I add a fourth 2TB drive. I understand it cannot be added to the original 3 disk set, but can be added as another device to grow it.

You can add it as another device in a pool by itself, but like the first 3, you cannot add more disks to *that* pool/vdev. Pools can have multiple vdevs (groups of disks or individual disks), BUT they must be the same size/grouping or you lose your redundancy.

Then I get to 6TB with 4 drives correct?

You would have 6TB of total storage, but they would be separate pools and the single disk would not have any redundancy. Like I said above, if you create another vdev with a single disk and add it to the first pool/vdev with 3 disks, then you ruin that pool/vdevs redundancy.

Do I still have the same data protection if I lose that new single drive?

NO

What I need is to be able to add drives from time to time and grow my storage, while still retaining the protection of drive failure.

Recomendations?

If you want the most storage for the drives you are talking about using, perhaps the better choice for you would be 2 ZFS mirrors. You could either have 2x 2TB mirrors with 4TB storage or group the 2 mirrors into a pool (stripe the mirrors), which I'm unsure about what you get for max storage in that conbination.


You could for learning purposes setup a virtual FreeNAS system in VMware and create some small virtual disks and play around with how they work and see what the different combo give you.

With ZFS you just need to plan ahead from the beginning, even with regular raid5 you can't really just add disks beyond a certain point, or use different sized disks.

 

[Fornax]

Hi Markhsa,

You'll be doing a fresh install of FreeNAS, so you can now change things if needed.
i3 with 8 Gigabyte of RAM is good. You appear to have 3 drives of 2TB, which is a good start, we'll add 1 2TB disk in a minute.
You HAVE to be able to grow your storage, which can be done.

What you share with FreeNAS over the network is called a Pool. This Pool consists of 1 or more VDevs, a group of drives. A VDev could very well be a Raid-Z1 of 2+1 drives like you described in your startingpost, which is a good choice. If you want to make your pool bigger you want to add a simmilar VDev to your Pool, so that would be another 3 drives (2+1 in Raid-Z1, these do not have to be 2TB, could be 3x1TB or 3x0,5TB but with the same structure as your other VDev).

You need dataprotection.

How about you create your Pool with mirrored drives? Make VDevs of 2 similar drives and add those to your Pool? You start your Pool with 4 drives and thus create 2 VDevs of 2 mirrored drives. If you need more storage you can now add VDevs to the existing Pool as needed by buying 2 drives a time. If you plan to add 2 terrabyte per year this is probably a good choice since you need to buy only 2 drives at a time. (After adding a new VDev move some date away from it, copy it to it, move other data away, repeat, this will distribute data over all the drives in the new pool.)

Initially you do loose a bit on maximum storage but when expanding later you need to buy less drives at a time.

 

[ProtoSD]

Wow, not sure what happened, but sorry for all of those duplicate posts. It happens once in awhile and I don't know why but I've deleted them.