Pool / vdev Advice :)

[Coolamasta]

Hi all, just wanted to see what peoples thoughts were on Pool/vdev design for mainly media storage. I am quite new to FreeNAS and how ZFS works, I have a bunch of 8TB drives already and want to buy some more but not sure what best config of pool should be for now and future expansion.

I plan to have 8 or 9 x 8TB drives total for now and want decent I/O over 10G network and also good redundancy, here's the options I have been thinking about for a single media Pool,

• 8 x Drives in single vdev in RZ2 (Cant think of a good reason to use this design?)
• 2 x vdev sets of 4 x Drives in RZ2 (Best Redundancy but a lot of lost capacity?)
• 2 x vdev sets of 4 x Drives in RZ1 (Good amount of capacity but higher failure risk?)
• 3 x vdev sets of 3 x Drives in RZ1 (Best I/O?)

From what understand from reading a bit more into ZFS, more vdevs will give better I/O but dropping to more vdevs in RZ1 is a greater failure risk as you can only lose a single drive so dropping to just a 3-disk RZ1 vdev rather than 4-disk might be best option, what are peoples thoughts?

Also can anyone answer this - just say for now I used 6 x 8TB drives in 2 x 3-disk vdevs and then filled them over half full and then further down the line added 3 x more disks in another vdev, will FreeNAS over time move some of the data from the existing 2 vdevs and balance it over the 3rd or will data just stay on the existing 2 and then start to fill up the 3rd vdev when the other 2 get filled up? Sorry if silly question but just after some clarification :)

Many thanks for any help.

 

[sretalla]

8 x Drives in single vdev in RZ2 (can't think of a good reason to use this design?)

Maximum capacity with dual-disk loss capability. Ample performance for Media files in most scenarios.
Minus is that to add additional drives, you should really add 8 more (although you could probably add only 4 in RAIDZ2 if you wanted).

Also can anyone answer this - just say for now I used 6 x 8TB drives in 2 x 3-disk vdevs and then filled them over half full and then further down the line added 3 x more disks in another vdev, will FreeNAS over time move some of the data from the existing 2 vdevs and balance it over the 3rd or will data just stay on the existing 2 and then start to fill up the 3rd vdev when the other 2 get filled up?

No automatic re-balancing. You would need to clear the Pool and restore all data once the new config was in place to have it balanced.

 

[Coolamasta]

Maximum capacity with dual-disk loss capability. Ample performance for Media files in most scenarios.
Minus is that to add additional drives, you should really add 8 more (although you could probably add only 4 in RAIDZ2 if you wanted).


No automatic re-balancing. You would need to clear the Pool and restore all data once the new config was in place to have it balanced.

Many thanks for your input @sretalla so in your opinion then the 8 drives in a single RZ2 vdev would be the best option for media storage? Would more vdevs in a pool really only be more suited for more I/O such as a VM host datastore?

Shame no automatic re-balancing but thanks for confirming that as definately will influence my final decision.

 

[sretalla]

so in your opinion then the 8 drives in a single RZ2 vdev would be the best option for media storage? Would more vdevs in a pool really only be more suited for more I/O such as a VM host datastore?

Yes and yes.

 

[HoneyBadger]

8TB drives

Post make and model please, I really hope these aren't shucked Seagate SMR units.

 

[HolyK]

so in your opinion then the 8 drives in a single RZ2 vdev would be the best option for media storage?

I second to that. 6-10 disks in Z2 is common practice. 8 seems to be a sweet spot but 10 is still ok. In case more than 10 i would consiser more than one VDEV.

I would not consider Z1 unless the data can be fully reconstructed from other sources or restored from backups.

 

[Coolamasta]

Post make and model please, I really hope these aren't shucked Seagate SMR units.

@HoneyBadger They are WD Red/White's which are MyBook Shucks, not been a fan of Seagate drives but out of interest are the SMR's particularly bad or something?

I second to that. 6-10 disks in Z2 is common practice. 8 seems to be a sweet spot but 10 is still ok. In case more than 10 i would consiser more than one VDEV.

I would not consider Z1 unless the data can be fully reconstructed from other sources or restored from backups.

@HolyK Thanks for your input, so maybe 8 x 8TB in RZ2 is the way to go then

 

[hervon]

Search "SMR" in the forums. Slow performance and very long resilver time.

 

[HoneyBadger]

are the SMR's particularly bad or something?

Yes; with drive-managed SMR you eventually hit a point where ZFS is writing into LBAs that is believes are free, easy writes, but in reality writing to them causes the drive to have to reshingle a full band (I believe all current SMR drives use 256MB zones) so picture the read-modify-write problem that exists with ashift=9 on 4K drives being extended to a "256MB sector size."