Pool Layout

[Fastline]

Hello Guys,

I'm having an old NAS and I'm planning to upgrade it to higher storage capacity. From 2TB to 10TB disk. There are 8 disks and here's the current configuration:

2 Vdevs consisting 4 drives each in RAID Z1.

My question is whether it would be okay to use it like that or should i use single vdev but RAID Z2 or 2 vdev consisting 4 drives each but RAID Z2. I've heard that RAID Z1 is dangerous. But in my above layout, i guess there are one each disk as redundant and if one drive fails from one vdev, or both, the pool will continue to operate. Is that correct?

I'm using Z1 for now as I'm getting the maximum speed after stripe.

Thanks

 

[tony95]

I definitely would go 8 disk Z2. If a disk fails during rebuild on the wrong side of a (4 + 4) Z1 then you are toast. Performance should be pretty good. You can try both and see if it will work for you. I tried a 10 disks (5 + 5) RaidZ2 and I didn't really see a performance difference but I still haven't figured that out. Please try both and let me know if you see a big difference. I would really like to know myself.

 

[Fastline]

I definitely would go 8 disk Z2. If a disk fails during rebuild on the wrong side of a (4 + 4) Z1 then you are toast. Performance should be pretty good. You can try both and see if it will work for you. I tried a 10 disks (5 + 5) RaidZ2 and I didn't really see a performance difference but I still haven't figured that out. Please try both and let me know if you see a big difference. I would really like to know myself.

Well, if i use 1 vdev that consists 8 disks in RAID-Z2, the speed results are 670MB/s Write and 1GB/s Read.

BTW, RAID-Z2 means 2 disk of redundancy so 2 vdevs which consists of 4 disk in Z1, that also means each pool has 1 redundant disk which means a total of 2 disk of redundancy? Or am i wrong here?

 

[tony95]

Well, if i use 1 vdev that consists 8 disks in RAID-Z2, the speed results are 670MB/s Write and 1GB/s Read.

BTW, RAID-Z2 means 2 disk of redundancy so 2 vdevs which consists of 4 disk in Z1, that also means each pool has 1 redundant disk which means a total of 2 disk of redundancy? Or am i wrong here?

Yeah, you are correct. What freaks me out though is if you lose a disk then during the rebuild process you have no redundancy in that vdev until it finishes building. With Z2 every disk is protected during a rebuild by the second parity disk. That speed for Z2 is pretty good, are you going to test the (4 + 4) Z1? Of course the speed will be a bit slower as the pool is filled with data.

 

[Fastline]

Yeah, you are correct. What freaks me out though is if you lose a disk then during the rebuild process you have no redundancy in that vdev until it finishes building. With Z2 every disk is protected during a rebuild by the second parity disk. That speed for Z2 is pretty good, are you going to test the (4 + 4) Z1? Of course the speed will be a bit slower as the pool is filled with data.

Yes, already tested it and also mentioned the speed in above post. With the 4+4 in Z1 is the fastest after stripe. RAID Z2 gets slower. Approx 600MB/s with 8 disks. I have also tried mirror and those had more lower speeds.

 

[tony95]

Yes, already tested it and also mentioned the speed in above post. With the 4+4 in Z1 is the fastest after stripe. RAID Z2 gets slower. Approx 600MB/s with 8 disks. I have also tried mirror and those had more lower speeds.

Sorry, I don't see where you list the two Z1 vdev speeds. Just that the Z2 was giving 670MB write and 1GB read.

 

[Fastline]

Sorry, I don't see where you list the two Z1 vdev speeds. Just that the Z2 was giving 670MB write and 1GB read.

Oh, sorry my bad. For 4+4 drives in Z1, I'm getting full 1GB/s Read and Write.