Understanding the nuances of ZFS

Inxsible · 2015-02-26 22:50:03

I am currently in the process of building a NAS server whose sole job would be to serve media files and storage of all the stuff I have. It might also act as a SCM repository for development work that I do on my desktop.

For the longest time, I planned on installing FreeNAS on a USB drive and utilize the internal drives for storage only. However, I have been reading up on ZFS and it seems that you need to have all the drives to be the same size in order to get the maximum storage space. My desktop currently doubles as a media server for my entire network and the whole reason to build a NAS was to utilize the 2 additional internal drives that I have lying around. The desktop I have only has space for 1 internal 3.5" drive.

The drives I have are :

80 GB Western Digital (this came with the desktop - ultra small form factor)
500 GB Western Digital (this was an external drive until the reset button on the external drive blew out)
1 TB Samsung Spinpoint (currently in the desktop)

I also might put a 500GB laptop drive in the NAS once my wife's laptop dies (its on its last legs having lasted 5 years).

I intend to put the 500 GB in the desktop and use the 1 TB and the 80 GB in the NAS box. The NAS case can support 6 drives and I will add them eventually but they still could be different sizes as I don't throw away my hardware unless it stops working altogether.

Can I still use ZFS and what would be the max space that I would get for storage between the 2 drives (80G and 1T) ? I did think about going FreeNAS with UFS -- but that would mean I would be stuck with an older version of FreeNAS since the latest 9.3 only supports ZFS. Also at that point, I think it would be better to just use Arch as a headless server installed in a USB.

ANOKNUSA · 2015-02-27 01:54:24

The requirements are mostly related to FreeNAS, not ZFS itself. Some thoughts:

1) As with BTRFS, you can create single-disk pools or multi-disk spans with ZFS, but it works best in RAIDZ configurations. I believe this is the default for FreeNAS, and it will get uppity if you use disks of varying sizes or JBOD configurations. You can span a ZFS pool across differently sized volumes if you set them up yourself, but you'll lose the redundancy and (maybe) a bit of performance.

2) ZFS friggin' loves RAM. Just has an irresistible craving for it. You can use ZFS on a machine with 2 gigs of RAM without any problems, provided you only use basic ZFS features like snapshots and RAID and basic checksums. If you want to use more advanced features or a setup that may add up to a lot of storage, though---like an NAS box---you'll want considerably more RAM. Features like snapshots with more stringent checksums and deduplication eat it up quickly. The FreeNAS documentation has a breakdown of the RAM and storage recommendations. They strongly recommend a minimum of 8 gigabytes of RAM. This isn't a requirement of ZFS, but FreeNAS is configured to make the most out of the storage pools it creates, with all the ZFS bells and whistles.

3) The Linux implementation of ZFS, to the best of my knowledge, has some fundamental differences from the FreeBSD/Solaris implementation. FreeNAS uses the latter, and I actually don't know much about the former. Information you get on Linux forums might point you the wrong way; I'd recommend the FreeNAS forums if you really wanted to go that route.

Inxsible · 2015-02-27 05:18:49

Thanks Anoknusa.

i did get 16G of ECC RAM which is the max the board will support. I did not know that the Linux implementation of ZFS might be that different than in FreeBSD/FreeNAS. It looks more like I will be setting up a headless Arch server with lvm and regular ext4 partitions and eventually when I get additional disks -- probably of the same size -- I might try a hand at FreeNAS and ZFS at that time.

Arch Linux

#1 2015-02-26 22:50:03

Understanding the nuances of ZFS

#2 2015-02-27 01:54:24

Re: Understanding the nuances of ZFS

#3 2015-02-27 05:18:49

Re: Understanding the nuances of ZFS

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