Infrastructure // PC & Servers
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6/8/2007
03:27 PM
John C. Welch
John C. Welch
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On ZFS As The Default File System In Leopard

I don't care what Sun CEO Jonathan Schwartz said, or how the Mac community interprets what he said, the idea that ZFS will be the default, boot FS in Leopard makes no sense.

I don't care what Sun CEO Jonathan Schwartz said, or how the Mac community interprets what he said, the idea that ZFS will be the default, boot FS in Leopard makes no sense.Now, that's not the same as saying ZFS has no place in the Mac OS. Indeed it does. But as the default boot consumer FS? No, I won't believe it until Jobs says it and I see it. Thus far, the only consistent statements for this come from Sun. Remember ATI.

There are some real problems with this.

First, ZFS is not designed for consumer use. It can be, during grooming and snapshot file deletion operations, rather CPU intensive. Mac users complain about Spotlight's CPU usage, they're going to lose their mind when their file system eats significant CPU resources on a regular basis just to perform cleanup duties.

Secondly, deleting in ZFS is not like deleting in any FS a Mac consumer is used to. First, you might not actually get that space back right away. In fact, under some fairly common situations, you may even see a decrease in free space following a deletion. The way ZFS does things is great for a sysadmin, or in LOLcatspeak: DO WANT NOW PLZ. But for home/consumer/nontechnical users? Not so much. I mean, I know Mac users are quite often unreasonable, but can you imagine the hell that this will put phone support/Geniuses through?

Thank you for calling Apple support, how can I help you today?

Ah, you have Leopard, you deleted some files, and now you have less free space than before, is that the problem you're reporting?

Right, well sir, that's normal for our new, improved file system. It will eventually go down.

Well, how long it will take depends on a lot of things, sir.

Sir, please, I've only one good ear left, and I think what you suggested I do with ZFS is neither physically or psychologically possible, and even as a concept is quite disturbing.

Thirdly, ZFS's block size is somewhat suboptimal for a boot drive. You can change it, but then you lose some efficiencies in other areas.

Fourthly, and more important, using FireWire/USB drives becomes a pain. No, really. If you use ZFS, then you have to deal with what happens when someone tries to plug it into a non-Leopard Mac. Mac OS X 10.4. Mac OS X 10.3. Earlier. Yes, yes, we should all be upgraded. However, that's not free, and if you have a setup that's working, you're not going to mess with it much. So how far back does Apple backport ZFS access, and at what level? Those of you around for 8.1 and HFS+ remember that it didn't work on anything earlier than 8.1, and it was a pain in the ass to remember what file system format to use. If you're a sysadmin, no big deal. But if you just want to use the thing?

Okay, so you don't allow ZFS usage on portable drives. That's not going to work, because what if you have a machine go dead but the drive's fine, and you want to use it on a different system temporarily? Normally, you use FW or USB on Intel Macs and take the performance hit, because that's really 90% of your problems. Maybe even 99%. But now you can't use that data unless it's an internal drive? How the hell do you even ENFORCE that?

If you don't backport it, then do you do a new version of the infamous HFS Wrapper with the text file that said "You can't read this drive, because your OS is wrong"? Yeah, right. So now you force people to do a major upgrade just to read a disk that they shouldn't have to think about, or, you start trying to make non-technical users care about FS formats. Or even more complicated, some wrapper that makes ZFS act exactly like HFS+ when needed? How do you even begin to test that.

Right now, there's no way to make issue four not stink. Come say...10.6 or 10.7? Different ballgame, you can phase it in. But as a scream and leap? Very Bad Idea.

Don't get me wrong, ZFS is a hell of a file system. It's probably the best new idea in FS's in a long time, and it has incredible potential. But it's not yet ready for prime time as a primary default consumer file system. On file servers? Oh hell yeah. I'd do it on my Xserve RAID's now if I could But not yet as a primary consumer filesystem.

Oh, and on Marc Hamilton's post:

Jonathan noted that Apple will announce this week that the ZFS file system from OpenSolaris will become Apple's new default file system. So how does that help Sun? It is pretty simple, now every Apple developer will know ZFS and how to use it on products like our SunFire x4500 storage server and other Sun products.

Well, first Marc, you're going to have to actually support Mac OS X as a direct client for us to use your zippity doo-dah storage products without the $30K NAS head stupidity or running through another OS as a front end, and two, you might want to see about you getting your post and your comment story straight. (Actually they are managing not to say "in Leopard" for this, but they aren't exactly working hard to not say it either.)

Also, ZFS support has nothing to do with Macs participating as direct-attach members of Sun SANS. For one, ZFS isn't a SAN FS mostly because in its current incarnation, it can't be a SAN FS. For another, the local boot OS on the client box is meaningless in a SAN. You support the OS/Platform, not the file system. Without the OS, the FS just sits there.

I think that if you read Schwartz's comments as "ZFS will be a filesystem in the Mac OS, and we're going to work with Apple to help make it the default FS one day", then things make a lot more sense.

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