What raidz configuration to choose?

[Umberto]

Some time ago I decided to let go of my Windows 2012 Essentials home server. It is a bit much for my use and I am fat up with keeping up with all the updates. I soon found out that a consumer NAS was not for me (for several reasons). So I started to look into alternatives (even tried Amahi). To make a long story short I go for FreeNAS. I have played around with it a bit on some old hardware and liked it (a lot).

Now it's time to dismantle my Windows box and dedicate it to FreeNAS. My hardware is OK and meets about all the demands for FreeNAS and ZFS. What's left is to decide about the configuration of my storage pool. And that is were things get a bit difficult for me. On the Windows box, I pooled my drives with Stablebit Drivepool and that worked OK for me. But working with ZFS will force me to rethink the way I am going to handle my drives.

I own 6 2TB WD red drives. The oldest one is about 2 years and they are all OK. There is no room (for now) on the budget to buy any more disks. I have done a lot of searching and found a lot of information. Problem is that I also found a lot of contradicting information. It's a hard job to weed it all out.

I found an article stating that I should never use Raidz (2/3) but would be better of with a pool of mirrored vdevs, Other articles and forum threads are raving about Raidz Raidz2, Raidz3 etc.
At this moment I think I need to choose between Mirrored vdevs or a Z2/Z3 configuration. Sources I have found are stating that you should start a Raidz2 with 6 disks or more and a Raidz3 with 9 disks or more (so Raidz3 is out for me?).

Here is my use case.
The FreeNAS box will be a file server and will be used to store backups of a couple of workstations/laptops.
The file server will hold my administration (business and private)
The file server will hold some media like ebooks, Music (Flac), photos and a limited number of movies.
At this moment my storage contains about 2 TB of data and I expect a growth of about 1 TB a year.

Of course I have a decent back up plan in mind (on site and cloud storage). I love my data.

What I would appreciate is to receive some thoughts/advice about the best configuration for my storage, keeping my number of disks and my use case in mind . Especially reactions of those of you who are working with a pool of 6 disks and your reasoning for choosing a certain configuration would help me out. Thanks in advance.

 

[Pitfrr]

I'm using a pool with 6 disks on both main and backup server and for both I'm using RaidZ2.
I find it to be a good compromise between effective vs. raw space.
I don't need to achieve specific performances so that's fine for me how it is.

My vision is that RAIDZ is not safe enough considering the sizes of the disks. RAIDZ3 is overkill for the usage I have (and the number of disks) so RAIDZ2 seems a good compromise.

 

[Robert Trevellyan]

I found an article stating that I should never use Raidz (2/3) but would be better of with a pool of mirrored vdevs

I always argue that the main advantage of mirrors for home users is flexibility. You should weigh that against reliability when considering your decision.

For example:

If you take your existing six 2TB disks and put them in three striped 2-way mirrors, you'd start out with a nominal 6TB of raw storage. When you need more storage, you can replace as few as two disks with larger disks. At the same time, if one disk fails, the chances of a 2nd disk failure destroying the pool would be 20%.

If you put those six 2TB disks in a single RAIDZ2 vdev, you'd start out with a nominal 8TB of raw storage. When you need more storage, you have to replace all six disks with larger disks. At the same time, if one disk fails, the changes of a 2nd disk failure destroying the pool are 0.

 

[Robert Trevellyan]

Sources I have found are stating that you should start a Raidz2 with 6 disks or more and a Raidz3 with 9 disks or more

Those sources are out of date. Ignore them.

 

[Robert Trevellyan]

I have a decent back up plan in mind (on site and cloud storage). I love my data.

:D

 

[nojohnny101]

I have 6 disks in a raidz2 configuration. As it has already been stated, for my purposes, Raidz2 was the right balance between redundancy and space lost to parity. @Robert Trevellyan makes some good points about the cost one incurs when it comes time to grow the pool (by either replacing disks or adding another vdeve of similar size) but to me the advantages outweigh this.

All the response you are going to get here are going to be opinions. From you research, you should at least know that there are no "wrong" ways to configure your storage, just some that make more sense then others depending on your situation. All of them are a balance between usable storage, redundancy, cost, etc.

Good luck!

 

[Umberto]

Thanks for sharing your thoughts people. I have decided to go with a Raidz2 setup. I feel that it would give me the right balance between reliability and needed data space. I just hope that if (or when :) ) a disks fails on me, the resilvering will not be to bad. A pool of 6 drives to me is manageable if it comes to the costs of upsizing, by replacing the drives with bigger ones later on.

With my 6 drives in RaidZ2 I should have sufficient space for the coming 2 years at least. Total raid space will be 12 TB. Parity will cost me around 4 TB. So 8 TB data space would be left. I would want to keep around 1.5 TB free space before ther is a need for upsizing. So that means more then 6 TB as usable data space. Not exactly a precise calculation I know, but good enough. Starting with 2 TB already occupied, there should be plenty of room for my estimated growth.

Crazy data rich world we live in by the way, my first hard drive ever was a blistering 10 MB

 

[Umberto]

All the response you are going to get here are going to be opinions. From you research, you should at least know that there are no "wrong" ways to configure your storage, just some that make more sense then others depending on your situation. All of them are a balance between usable storage, redundancy, cost, etc.

Good luck!

You are right. But I value opinions. It helps with my thought processes.

 

[nojohnny101]

For a more accurate estimate of usable space you will get from various configurations, entire your data in this useful calculator:
https://jsfiddle.net/Biduleohm/paq5u7z5/1/embedded/result/