Recommended raidz2 array setup

[Oded]

Hi all,
Read many discussions on these forums regarding raidz2 setup but I am still not sure what would be the best path to take in my case.

My setup:

Silverstone DS380 - can hold 8 3.5" disks, 4 2.5" disks
ASRock C2750 mobo+processor
32gb Crucial ECC RAM

I want a setup that will allow me to have a very good redundancy for my crucial backups (mostly pictures), but also have excellent performance while streaming to HTPC full-size Bluray disks.

My current old setup stutters a lot and I want to avoid it this time.

It is my understanding that for RAIDZ2 it's recommended to use 6 or 10 disks but I didn't see any reference to an 8 disks config. Is it recommended?

If it would be of any use, I am thinking about a setup where I'll have 6 disks for Raidz2, and a different pool in Raid0. I would use the raid0 for streaming movies. I don't really care about redundancy for these files, I can always rip them back if needed. How much of a performance improvement do you think I'll gain if at all with a 2-disk Raid0 vs a 6-disk RaidZ2? I'd imaging it might be the same thanks to the shared speed of 6 disks vs just 2.

Option 3 is to start with a 6 disk array of raidz2 (6x4tb RED drives), and when needed add another set of 6x2tb RED drives. I'm pretty sure 2tb 2.5" drives are just around the corner, there are already 2.5" 1.5tb hitachy drives (I own one and it's great). The only issue is that in the final config this will result in a 36tb system (before parity) so 32gb of RAM might be too low and I'll need to upgrade to 64gb.

So, my options are:

1. 6x4Tb RED drives raidz2.
2. 6x4Tb RED drives in raidz2 + 2x4tb RED drives in raid0 as seperate pool.
3. 8x4Tb RED drives in raidz2
4. 6x4Tb RED drives in raidz2+6x2tb drives in raidz2 (when available in the future)
5. 2x(3+1) raidz1 setup, total of 8 disks but each vdev has a risk of one disk failure.

 

[Ericloewe]

Using 8 disks in RAIDZ2 leads to reduced performance, but it's typically not much of a problem. It's a problem for greater workloads, tough.

32GB should be plenty for 36TB, but again, you may need more for heavy workloads.

 

[solarisguy]

6x WD Red 4TB drives in raidz2. However..., instead of adding any more disks to this system, budget for an upgrade to 6TB disks.

 

[Oded]

6x WD Red 4TB drives in raidz2. However..., instead of adding any more disks to this system, budget for an upgrade to 6TB disks.

Thanks. What is the reasoning for this? does it become too much for a system to handle when you move to 12 disks (2 separate VDEVs in one ZPOOL)?

 

[solarisguy]

Your system does not have room for twelve 3.5" disks.

RAID, including one with 2 separate VDEVs in one ZPOOL, should have the same or similar disks (since data is stripped across both VDEVs). In my opinion, there are no 2.5" drives with performance characteristics similar to that of 3.5" drives, and when 4TB laptop hard drives hit the market, they will not behave the same as current 3.5" Reds, Greens or Blacks.

 

[Oded]

I doubt we'll see 4tb 2.5" drives any time soon... but I think 2tb drives are just around the corner, which is why plan a 6x2tb for the second VDEV. WD already makes a RED drive in 1tb capacity:

http://www.amazon.com/dp/B00EHBES1U/?tag=ozlp-20

But you're right, I didn't consider the possibility of different performance characteristics between 2.5 and 3.5. The only review I could find on the slim RED drives is this, but it's not comparing it to the big boys:

http://www.storagereview.com/wd_red_25_1tb_hdd_review_wd10jfcx

I think I'll stick with 6 drives for now and make up my mind later when there's more information available.

 

[solarisguy]

Actually quoted by you Storage Review article shows that performance of 1TB 2.5" Red drives differs from that of 4TB 3.5" variety.

2TB laptop drives are on the market:
http://storage.toshiba.com/storagesolutions/specialty/mq01abb-series
http://www.wdc.com/en/products/products.aspx?id=830

I still think that if you do not need lots of disk space now, then you should buy larger disks later.