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RAID choices for NAS

J

jdd561

n00b
Joined
Apr 3, 2014
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54
So I've recently decided to dive head first into the ZFS world, and built a shiny new NAS do it. My current plan is to fill up my 5 bay chassis with 5TB disks, as they seem to be at the pricing sweet spot for the moment.

So I have 5x 5TB drives on the way, and I am deciding whether RAIDZ1 or RAIDZ2 is the way to go.

The NAS will be almost exclusively serving as a media streamer and network backup. I do plan to continue maintaining my external copy of media/backup, so I have a backup system in place.

My understanding is RAIDZ1 will net me ~20TB usable space, and the ability for one drive to die and not lose my data. RAIDZ2 would net me ~15TB data and could survive 2 disk failures. I currently only use ~2.5TB of data, so I'm definitely building for the future - I don't want to have to invest in hardware again for a very long time.

Thoughts? Comments?
 
Your calculations on usable space is off.

raidz1 on 5 disks, will give you 4 disks usable, 20tb.

But usable space is going be down around 16-17tb, likely up around 17tb with your media files.

raid2 is going net you 12tb usable.

It all comes down to how paranoid you are, and if you don't mind spending the time to rebuild from backups. At 3tb, restore from backup isn't horrible, but when you get up around 10-13tb, you might rethink that idea, so plan for that usecase.
 
I'm going to vote for the Raidz2 option, largely because I don't want to spend the better part of a week restoring 12TB+ from my backup server over 1gbps ethernet. Backups are awesome, but... I don't ever want to have to use them.
 
Raid is not backup.
Nearly no discussion where you do not hear this phrase.

But when we talk about 20 TB, 200 TB or more then backup can only be disaster backup as a full backup/resore can last days or even weeks.

You must care about an as secure as possible primary storage. I would also prefer raid Z2
 
My instinct right now is to take the capacity hit and go RAIDZ2, as I'm still more than tripling what I currently use for capacity, and it's taken me ~6 years to build up to this.

My actual backup solution (until it is too small) is a USB drive that I could connect to the NAS using USB 2.0, so *hopefully* initial copy and rebuilds won't take *quite* as long as over gigabit.
 
USB 2.0 transfers at 480 megabits per second, which is just under half of gigabit. USB 3.0 transfers much faster though!
 
Ouch! I knew USB 2.0 was slower than USB 3.0....but forgot by how much!
I may simply temporarily use an SATA port to populate the data then. My avoton board doesn't do USB 3.0.
 
A modern disk has an average sequential performance of about 150 MB/s. In the inner area or with small files this drops to 10-50 MB/s (below USB2)
 
FYI if you're using FreeNAS, that's what I'm using ZFS and raidz2 just to let you know, FreeNAS will start giving you warnings if you use more than 80% of your pool. And my friend found out the hard way that when you go over about 90% the system will actually perform sluggish.

my 2 cents.
 
Go with RAID-Z3 and more drives, you'll be glad you spent the extra money when you have a failure.. and then a drive fails when you go to recover. I just went through this with used 1TB drives from an eBay seller in an MSA60 drawer and if I didn't have Z3 I would've lost all my data! Or setup a mirror with a hotspare.

You can always do 10GBe cheap, ConnectX2 Mellanox cards are really cheap. I have 10GBe at home now, and it's great for stuff like this (my file server runs dual Opty 4284s, has 80GB of RAM and 8 10GBe ports so I can hook directly to the clients)
 
I figure by the time I get anywhere near 80% usage, I'll be replacing all my drives due to age anyways. I went with RAIDZ2, which is a fair bit slower than the RAID0 stripe I had running before, but obviously not nearly as risky. So far works well for my needs.
 
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