Newbie FreeNAS build (old PC components vs. new server components)

[Yorick]

EDIT: Can I also add smaller drives in the same configaration as the other vdevs?

What do you think?

You can always add another vdev with drives of a different size, but the same type of vdev as the rest of the pool to keep redundancy.

Let’s discount raidz1, too scary. The chance that this fails on you during resilver is non trivial.

raidz2: Good redundancy, is highly likely to survive a resilver. Great storage efficiency. Expensive when expanded by drive replacement, as all 8 drives need to be replaced. Expanding by adding vdevs would also require 6-8 drives at a time.

mirror: fast resilver, storage efficiency low. Affordable when expanded by drive replacement, as 2 drives can be replaced at a time. Expanding by adding vdevs only needs 2 drives at a time. Much better performance than raidz2.

For flexibility, expansion options, and performance, mirror wins. It all depends, as always, on your use case and future expansion plans.

 

[sretalla]

The mirrored pool would be easier to expand (and fail safer?

If you have 2 drives fail amongst the 4 mirrors, , there's a non-zero chance that both of them are in the same VDEV... total pool loss.
For the 2x RAIDZ1 that's actually a higher chance of total pool loss with 2 failed drives.
For RAIDZ2, that's not a possibility, 2 drives failing is always tolerated, no matter which ones.

If it's just for archiving, I don't see why you would be too concerned about IOPS and for expandability, you can still upsize the disks at a later date (swapping them out one by one).

EDIT: Can I also add smaller drives in the same configaration as the other vdevs?

Yes, VDEV sizes/drive sizes don't need to be identical.

 

[Tobsen]

mirror: fast resilver, storage efficiency low. Affordable when expanded by drive replacement, as 2 drives can be replaced at a time. Expanding by adding vdevs only needs 2 drives at a time. Much better performance than raidz2

I like the ability to add 2 drives at a time to expand. But what about pool loss if one vdev fails as @sretalla said?

 

[Tobsen]

If it's just for archiving, I don't see why you would be too concerned about IOPS and for expandability, you can still upsize the disks at a later date

Yep, for archiving video files (raw data), but it will grow continuously. Buying 8 larger drives is quite expensive at once which is what I am afraid of...

 

[Etorix]

I like the ability to add 2 drives at a time to expand. But what about pool loss if one vdev fails as @sretalla said?

But you won't like that mirrors take 50% of storage capacity for redundancy. And the worst is yet to come: If one drive fails, any unrecoverable error from the remaining drive will result in total pool loss; no need for a second full drive failure. How likely is such an URE?
With the stated 1e-14 rate of WD Red drives, 38% for 6 TB to resilver, 47% for 8 TB, 55% for 10 TB (which is about the practical maximum that a 14 TB drive should be filled).
With a rate of 1e-15, as advertised by WD Gold and Seagate, 4.6% for 6 TB, 6.1% for 8 TB, 7.7% for 10 TB. Better, but not fully safe.

RAID5/RAIDZ was called dead some years ago for drives over 1 TB. We now have drives larger than 10 TB and this point 2-mirrors aren't safe either: It takes THREE-way mirrors or RAIDZ2 to protect from pool loss after a single drive failure.

If your hardware list hasn't changed, and you haven't build yet, 8*14 TB in a single RAIDZ2 gives 84 TB of raw space (minus ZFS overhead), which may hold about 60 TB of actual data before you have to worry about expanding—but then, optimally by another 8 drives. Else you could do a 6-wide RAIDZ2 with 6*14 TB (56 TB) and a second RAIDZ2 vdev with 2*14+4*4 TB (16 TB at start), and then progressively replace the 4 TB Ironwolf by larger drives. Upon replacing the fourth Ironwolf by a 14 TB drive, your pool will instantly grow from 72 TB of raw space to 112 TB.

 

[pschatz100]

I would agree that an 8 drive RaidZ2 vdev is a good balance between capacity and resilience against loss. I am a believer in RaidZ2 and don't see the value of multiple mirrors unless you need the performance (which you don't for an archive system.)

While everyone in this thread is stressing the requirement to update all the disks in a vdev to increase the capacity of a pool, there is no requirement that a FreeNAS system have only one pool. If you hit the capacity of your initial pool, then you can always consider adding a second pool. I will agree that one large pool is easier to manage than multiple pools - but at the end of the day, you still have options.