Best setup for small home NAS

[Thomas Haggren]

Hi all

I have some spare parts/hardware and want to turn this into a NAS at home. It will be used for movies, music, pictures, documents etc. Simple home usage with 3 clients connected to it.

Hardware:
- Dell Optiplex 760, Intel Core 2 Duo E8400 (3GHZ), 6 GB ram
- 3 x 2TB WD (SATA3)
- 1 x 1TB WD (SATA2)

Before looking deeper into what Freenas has to offer I was thinking of configuring the 3 x 2TB disk as RAID5, but after reading many threads and blog entries I can see that ZFS RAIDZ might be a better choice.

From what I understand I will in both cases end up with approx 4TB storage - correct?
ZFS RAIDZ seems to be a little slower than the RAID5 setup - correct?

Could I use the 1TB for any of the "ZFS extra" options supported by Freenas (seems like the "spare" option is not really an option in this case).

So guys... I'm not really sure what to choose here... any comments/help/advice would be very much appreciated

(I will be doing "offline" backup onto 2 x 2TB external USB discs).

 

[Milhouse]

Pretty much as you've worked out already - using 3x2TB and RAIDZ1 (one parity disk) you'll have 4TB of usable storage. Not sure what you can do with the 1TB disk, but if you replace it with a 2TB you'll have 6TB of usable storage. Or if you went with RAIDZ2 - two disk parity - and 4x2TB you'll have again 4TB storage but increased redundancy.

You could configure 3x2TB RAIDZ1 with a single 2TB hot spare, but this isn't really much different from 4x2TB RAIDZ2 - in fact, it's inferior as you could lose a second active disk while bringing the hot spare online (it will take several hours to sync the data from the remaining two disks), which would mean you lose all your data. Whereas with 4-disk RAIDZ2 your array would continue to remain available even with two dead disks.

Perhaps you could use the 1TB disk for a ZIL (logging) or L2ARC (cache) but it may not be fast enough to make a difference, as usually SSD's are recommended for this purpose, and always in mirrored pairs for redundancy - if you lose the ZIL or L2ARC disk, you lose access to your entire array until the ZIL/L2ARC disk is replaced.

So in your case, with no option to mirror the 1TB disk, I'd say it's not recommended and you forget about using a 4th disk, or you should upgrade it to another 2TB disk and then you can consider 4-disk RAIDZ1 for 6TB storage, or 4-disk RAIDZ2 for 4TB storage. However, since your external backup option only has a capacity of 4TB, I guess RAIDZ2 is the obvious choice - or stick with 3-disk RAIDZ1.

 

[Thomas Haggren]

Hi Milhouse

Thank you for the extended reply :) It seems I got the basic understanding in place.
I will start with a 3x2TB RAIDZ1 and then use the 1TB as a single point of failure share for BT seeding etc.

Is it possible to upgrade the RAIDZ1 to a RAIDZ2 just by adding a 2TB drive and make the array sync to the new disc?

 

[Milhouse]

Is it possible to upgrade the RAIDZ1 to a RAIDZ2 just by adding a 2TB drive and make the array sync to the new disc?

No, once you have created the vdev (which is the "collection" of your 3 disks) it's not possible to add additional disks and change the level of redundancy.

To expand your zpool (your storage), you either add additional vdevs (ie. a second group of disks, perhaps a mirrored pair or another 3 disks/RAIDZ1 etc. with data automatically striped across both vdevs), or you replace the 2TB disks one at a time for 3TB disks (although I don't think this latter option is currently supported by FreeNAS, at least not automatically so that the storage expands when the third and final disk is replaced).

If you do want to convert from a 3-disk RAIDZ1 to 4-disk RAIDZ2, you would have to delete the ZFS pool and restore all your data from backup.