What I would like from ZFS

You can read the Wikipedia entry here on ZFS to get an idea on what the file system offers and its real eases as well.

From using ZFS on my FreeNAS there is one thing I would like to see added that would really “take it up a notch” in my book: the ability to add a disk to  RAID-Z.

What I’m talking about is this situation:

  • You have four external drive bays
  • You fill three with 2 TB drives and setup RAID-Z
  • You get a fourth 2 TB drive and plug it in
  • You add it to the original RAID-Z and ZFS takes care of the rest

It is a lot like what Drobo has going for it, but on the file system level. You could add an arbitrary number of additional drives and ZFS would resize and just take over from there.

That would be really cool.

4 replies on “What I would like from ZFS”

Been watching ZFS for a while now but never been convinced to pull the trigger on using it in any of my systems. A big hold back was the fact that there’ve been a few reports of it fatally corrupting arrays. Granted that seems to only apply to software RAID, not hardware. Since I can’t afford good RAID adapters I’d probably have ended up using software RAID.

With storage virtualization these days I’ve come to the conclusion that the underlying FS doesn’t matter as much any more. As long as it is relatively fast and stable while all the other bells and whistles are taken care of at the software layer in your storage solution. Your OS doesn’t care about how those extra features are delivered since it just sees a block-level device.

Microsoft’s Storage Spaces solution seems to be pretty close to that you describe regarding the expansion. You still have to manually intervene unlike the Drobo but it doesn’t much care about what you’re adding for storage hardware. I’m a Windows Home Server fan and its great to see them offering a solution like the Drive Extender they had in the first firstions of WHS.

You are ALWAYS going to find reports of something getting corrupt … we’re talking about computers here, and the law of averages dictates that things go wrong. That is why we backup.

I think file systems are more important now more than ever because we keep housing more and larger stuff into more and larger drives and the file system needs to get into the habit of making sure that the stuff is all there, all good, and will be able to be retrieved if you need to get at it in … seven years? More? We’re talking about keeping pictures of our kids on these devices, and I would feel more comfortable if my file system that I am using would be doing at least some rudimentary checking of the data it is storing.

You can add devices to a storage pool in ZFS, that’s not the issue, what I would like to do is be able to setup a RAID-Z and then add a disk to the RAID-Z. Sadly, ZFS is meant for HUGE amounts of data, and if you are working with that amount of data, adding a single drive is silly so it isn’t a huge priority.

I wish I knew more about the secret sauce of Drobo to know exactly what they are doing.

Also, not using Windows. I’ve finally exorcised those demons from my own home. 😉

Drobo has some nice info on their site about the “secret sauce”. I haven’t reviewed BeyondRAID docs for a while so I’m pretty fuzzy on the details but I don’t recall anything being to wildly outrageous.

I guess if we’re talking pure data integrity then most active file systems are a poor fit for long term storage. Perhaps an archival file system or other WORM style hardware is more appropriate? Data checking is a difficult thing for an FS that also has to balance other factors such as performance at the same time. In my experience, most modern file systems do just fine most of the time.

The beauty of Drobo or even the Windows solution is the ease of adding those extra drives. Drobo does some acrobatics when extending an array. The MS solution however just mirrors files on separate file systems. Not efficient and not elegant by a long shot, but it does address some of the issues that arise with potential FS corruption by not mirroring blocks.

Totally respect the Windows aversion. Its just the world I live in.

I live in the same world.

I hear you on the performance issue, but what else should a file system be doing besides making sure things are working like they should. I admittedly don’t know enough about file systems to really be that informed, but if I’m going to take a performance hit I would rather take it for file integrity than unneeded features.

I’ll have to look at the Drobo docs again, they have the ease-of-use thing down but I’ve heard of WAY more issues with corruption with the Drobo devices than I have of ZFS.

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