First Time Build - Storage Question!

[Noah0504]

So, I finally decided to dig in and start researching for my first FreeNAS build. I've pretty much settled on the following hardware:

Case: Fractal Design Node 304 (Might change to something a little bigger.)
CPU/Motherboard: ASRock C2550D4I
RAM: 4 x 8GB of Crucial ECC DDR3 1600
PSU: SeaSonic SSR-450RM (450W 80-Plus Gold)

Now, let me get to what I'm still trying to figure out. I'm going to go with Seagate 4TB NAS drives, but I'm just not sure how many or how I'm going to configure them. I initially thought I would go with 4 and then configure them with RAIDZ2, but after hours and hours of reading, I'm not sure that's the way to go. I've seen a lot of people say RAIDZ is a terrible thing and mirroring is the only way to go, but there are also enough people who disagree with that as well.

Another suggestion I saw was to use two vdevs of 3 drives in RAIDZ1. This seems pretty clever because it would be easier when replacing drives to increase the size of a vdev -- just three drives at a time -- but, if 2 drives in one of those vdevs fails -- well...

So, because of that, I kind of want to stick with RAIDZ2. But, I was wondering if it would be possible to mirror two vdevs, so I would have two vdevs of 3 drives in RAIDZ1 that are mirrored. This would eliminate having to worry about a two disk failure and offer even more redundancy.

I could ramble on with possibilities, but I guess I want to know what everyone recommends. I might pull the trigger on this purchase this weekend, so I need to figure out the storage issue. I know I'm going to go with 4TB drives, and I can get 3-5 of them. What's everyone think?

 

[Jailer]

You sound like fault tolerance is important to you so I would go with a single 6 drive RAIDZ2 vdev. It's a good compromise of storage space vs redundancy. And speaking from experience go with the largest drives that you can afford. If I had it to do over again I would have started with 6TB drives instead of 3TB drives for my build.

I personally wouldn't go with Seagate but that's just my opinion.

 

[Noah0504]

Eh, I've always used Seagate with good results. I know a lot of people like the Reds, but anyway...

6TB drives are just a little too pricey for me at the moment, considering 6 4TB drives with everything else is pretty much all of the budget I allowed myself. But, that would leave me with 16TB of storage -- which would be plenty for a long while.

 

[Jailer]

considering 6 4TB drives with everything else is pretty much all of the budget I allowed myself

If that's what you can afford then go for it. You'll be glad in the long run that you did.

 

[Mirfster]

But, I was wondering if it would be possible to mirror two vdevs, so I would have two vdevs of 3 drives in RAIDZ1 that are mirrored. This would eliminate having to worry about a two disk failure and offer even more redundancy.

Kind of a waste of space if you ask me... if you use mirrors; then you are only getting half the space. Running RaidZ1 only gives you the redundancy of 1 drive. You can get two drive redundancy as well as more usable space with a single RaidZ2 vdev of 6 drives...

Roughly speaking:

• A single RaidZ1 vdev of 3 x 4TB drives = ~6.3 TB Usable Space
  • Mirroring this doesn't give you any extra space
• A single RaidZ2 vdev of 6 x 4TB drives = ~12.6 TB Usable Space

Check out @Bidule0hm 's "ZFS RAID size and reliability calculator" it will help you figure out things.

 

[Robert Trevellyan]

I was wondering if it would be possible to mirror two vdevs

You can't mirror vdevs with ZFS.