New Build - RAIDZ Question

[PETROLCAN]

Hi There,

Have recently just bought and fitted the parts together for my FreeNAS box and needed some advice on the RAIDZ implementation, this will mainly be used for storing moves,iso and music files of varied sizes.

I got 7 drives at 3TB each, I need atleast 9TB space, I initially did a RaidZ 2 setup but wasn't entirely happy with the performance so I wanted to see if there's something else I could do.

So I went through the Volume Manager configuration and did like this:

Set 1 = RAIDZ - 3 Drives

Then used the "Add Extra Device" to add the below:

Set 2 = RAIDZ - 3 Drives

Then used the "Add Extra Device" to add the below:

Spare = 1 Drive

The idea was then to combine the 2 sets into a Stripe, however when I finished, it created only 1 entire set(see picture attached), so I don't know if it's already Striped them ?

Also as I understand it, each RAIDZ can sustain 1 drive failure ?

 

[HoneyBadger]

ZFS vdevs can only be striped with one another, so if you started with one RAIDZ of three drives, and added a second, it would be striping the second one into it. You can see that via the total raw size of your pool.

But if that image is correct, the pool is 98% full? That kind of usage will make anything crawl.

 

[danb35]

No, it looks like he's created a dataset within the pool called RAIDZ, maybe with 10.5 TiB of reserved space? Not quite sure what's going on, but you'll note that the dataset also says it has 10.5 TiB available.

@OP, you should have been easily able to saturate a gigabit with those disks in RAIDZ2, which would be the much more robust configuration. What's your hardware like, and which version of FreeNAS are you running?

 

[PETROLCAN]

Hiya,

Thanks for the reply's, this is a brand new setup, yes for some reason it said 10.3TB used(98%) however next to it, it says 10.5TB available, I'm currently playing about with the config before I start copying data to it, it's empty at the moment.

@danb35

So the hardware I got last week is as follows:

Silverstone DS380
300W SFX PSU(think it was Silverstone)
ASRock Rack C2550D4I
16GB RAM(4 X 4GB @ 1600Mhz, Non ECC), I know ECC is important, will look into in the future.
7 x Seagate 3TB 3.5" Drives
16GB USB Stick for FreeNAS
FreeNAS-9.3-STABLE-201504100216

I went ahead and re-created the set, took a picture of it this time so you can see exactly what I did, what you see in the picture attached in this post, created what you see in the picture in the first post. with RAIDZ2 I was getting about 50-70% utilization on a single GB link, when I setup what I did in the picture attached, speeds seem to be a bit better. With RAIDZ2, a single 50GB ISO starts at a burst of 250 MB/s or so, eventually drops to around 60 MB/s, with the setup I did in the attached pic, it drops to around 80 MB/s sustained.

Also, I have a 256GB SSD laying around, would it help to add it as a ZIL ?, I've read very mixed points on if a ZIL helps or not.

 

[SweetAndLow]

The z2 configuration should saturate a gigabit link so I suggest using that. And also don't use z1 it's not best practices to use it. Just transferring a file isn't a good way to test performance. You need to look at network speeds, then local disks speeds and src client speed to actually figure out your bottleneck.

 

[HoneyBadger]

An SSD for ZIL, or SLOG in proper terms, will only help for synchronous write loads. CIFS isn't sync by default so it likely won't do you any good.

 

[PETROLCAN]

@HoneyBadger,

Apologies, I meant a L2Arc not a ZIL, I tried this anyway, it seems to give me about 6-10 MB/s improvement but it's not much. I get about 80% network usage.

 

[cyberjock]

@HoneyBadger,

Apologies, I meant a L2Arc not a ZIL, I tried this anyway, it seems to give me about 6-10 MB/s improvement but it's not much. I get about 80% network usage.

Well, duh. As we've said over, and over, and over, and over... unless you have lots of RAM.. (aka >32GB of RAM) an L2ARC is a fool's errand. It can (and probably will) hurt performance.

 

[HoneyBadger]

Don't add a 256GB L2ARC with only 16GB of RAM. The index will consume a pretty sizable chunk of memory and will likely hurt performance overall as @cyberjock states.