7x8TB Drives and 16 Bays - WWYD?

[scruzloose33]

I am building out a new FreeNAS server in a 16-bay Supermicro chassis. I happen to have seven WD 8TB red/white drives. I see my options as:

1. Use six drives in a RAIDZ2 and keep one cold or hot spare drive. I’m not crazy about leaving a drive on the shelf, even though I know it is recommended. This is for home use, so I could keep the server off while I purchase (or RMA) a new drive to replace a failed drive.

2. Use all seven drives in a RAIDZ2. This increases storage to a more desirable level, but leaves me with an awkward number of remaining empty bays in the chassis. I suppose I could eventually fill them out with a 9-disk RAIDZ3, but my understanding is that a matching vdev would be preferable if I would plan to add the next vdev to the same pool. Another option would be to build two 7-drive RAIDZ2 vdev’s and save the extra two bays for my OS SSDs or a basic 2-drive mirror (that I would put into a new pool).

3. Go buy another 8TB drive and build an 8x8TB RAIDZ2. I think 8 drives is pushing the limit of my comfort with RAIDZ2, especially with such large drives. My next vdev could then be a matching 8x8TB vdev.

What would or wouldn’t you do? I know this decision is somewhat subjective, but I am hoping the more experienced users can help eliminate some options that are a bad idea or suggest another option that I haven’t considered.

 

[Constantin]

I went for a 8-drive Z3 because I'm paranoid. Plus, this arrangement allowed me to use the same types of drives for both the array and the 5-drive backup array (which is RAID 5) while also respecting the "fill the pool no more than 80%" FreeNAS rule.

So I get 4 drives worth of effective space, with the other 4 drives either providing parity or the 20% space that should be kept free for FreeNAS. That in turn allows me to only stock one type of proven spare drive. Not ideal from an efficiency / speed POV but hopefully fairly bulletproof re: data integrity. If Z2 is "good enough"I see nothing wrong with doing a 7-drive Z2 array. Esp. if you plan to fill one ore more of the drive bays with a SLOG or L2ARC SSD.

My current server features two SSDs for the SLOG (mirrored), and a L2ARC cache, all of which consume one SATA data port each. Add the FreeNAS / FreeBSD SATADOM and only 8 SATA remain "open" on the C2750D4I motherboard. They are all in use now. Your motherboard may or may not have more SATA channels available...

That said I would always keep a proven, cold spare drive on hand. The RMA process may take weeks, drive shortages have occurred thanks to natural disasters, etc.

 

[bollar]

I like 3. Option 2 with 7 drives in RAIDZ2 would allow you to replace failing or upgrading drives without pulling the source drive.

 

[Holt Andrei Tiberiu]

I have simiilar setup , a I have a 4 x 7 drive raidZ2. it works well, i use it for storage, large video files and backup.
You can go with 7 x 8TB in raidZ2.
If you want to use ISCSI for VM's, go with 3 x 2 Drives in Mirror and leave 1 for spare.

 

[danb35]

I'd lean toward option 3, assuming you're looking to do bulk file storage on this machine. If your primary use case is block storage, striped mirrors would be the way to go for performance.