• ZFS
    May 4, 2006

You say zeta, I say zetta

Guest Author

On a lighter note, what is the Z in ZFS?

I've seen the (non-)word 'zetabyte' many times in the press. It's also been noted that zeta is the last letter of the Greek alphabet, which will no doubt surprise many Greeks.

So, here's the real story. When I began the (nameless) project, it needed a name. I had no idea what to call it. I knew that the Big Idea was to bring virtual memory concepts to disks, so things like VSS (Virtual Storage System) came to mind. The problem is, everything I came up with sounded like vapor. I don't know about you, but when I hear "Tiered Web Deployment Virtualization Engine" I assume it's either a vast steaming pile of complexity or a big fluffy cloud of nothing -- which is correct north of 98% of the time. So I didn't want a name that screamed "BS!" out of the gate. That actually ruled out a lot of stuff.

At first I was hesitant to pick a name that ended in FS, because that would pigeon-hole the project in a way that's not quite accurate. It's much more than a filesystem, but then again, it is partly a filesystem, and at least people know what that is. It's a real thing. It's not a Tiered Web Deployment Virtualization Engine. I figured it would be better to correct any initial misimpression than to make no impression at all.

So the hunt was on for something-FS. The first thing I did was to Google all 26 three-letter options, from AFS to ZFS. As it turns out, they've all been used by current or previous products, often many times over. But ZFS hadn't been used much, and certainly not by anything mainstream like (for example) AFS, DFS, NFS or UFS.

I should mention that I ruled out BFS or BonwickFS, because it implies either sole authorship or a failure to share credit. Neither would be good.

So in the end, I picked ZFS for the simplest of reasons: it sounds cool. It doesn't come with any baggage, like YFS (Why FS? Ha ha!). And you can even say it in hex (2f5).

The next task was to retrofit the acronym -- that is, I had to come up with something for the Z to stand for. I actually got out my trusty old 1980 Random House Unabridged and looked through the entire Z section, and found nothing that spoke to me. Zero had a certain appeal (as in zero administrative hassle), but then again -- eh.

OK, what does the web have to say? I don't recall exactly how I stumbled on the zetta prefix, but it seemed ideal: ZFS was to be a 128-bit filesystem, and the next unit after exabyte (the 64-bit limit is 16EB) is zettabyte. Perfect: the zettabyte filesystem.

A bit of trivia (in case the rest of this post isn't quite trivial enough for you): the prefix 'zetta' is not of Greek or Latin origin --
at least, not directly. The original SI prefixes were as follows:



















The demand for more extreme units actually began at the small end,
so the SI people needed names for 1000\^-7 and 1000\^-8. For seven,
they took the Latin "sept" and made "zepto" (septo wouldn't work
because s for second is ubiquitous); for eight, they took the Greek
"okto" and made "yocto" (octo wouldn't work because o looks like 0).
For symmetry with zepto and yocto on the small side, they defined
zetta and yotta on the big side. (I also suspect they were drinking heavily,
and thought yotta was a real hoot.)

But zettabyte wasn't perfect, actually. We (we were a team by now) found that when you call it the zettabyte filesystem, you have to explain what a zettabyte is, and by then the elevator has reached the top floor and all people know is that you're doing large capacity. Which is true, but it's not the main point.

So we finally decided to unpimp the name back to ZFS, which doesn't stand for anything. It's just a pseudo-acronym that vaguely suggests a way to store files that gets you a lot of points in Scrabble.

And it is, of course, "the last word in filesystems".

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Comments ( 3 )
  • ux-admin Thursday, May 4, 2006
    I love your tidbits (honestly, no joke). I wish you'd write more often on this (and other) stuff, but I guess you're too busy perfecting that genious ZFS thing you guys have going on.
  • Todd Monday, May 8, 2006
    Christ, nothing for months, then two in two days? As I look around, it seems everyone took a blogging vacation from last December to late April. Tell me it's because you're porting ZFS to Debian or OS X. [ducks] Keep it up!
  • Jim Tuesday, May 9, 2006
    I guess ΩFS was already taken?

    I'm looking forward to ZFS on my mac.

    I can't wait to try ZFS send/receive.

    How soon before we can boot from a ZFS volume?

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