Sun's new file system for Solaris 10. Apparently unrelated to
Even Moshe Bar (author of Linux
File Systems) seems impressed: http://www.moshebar.com/blog/?q=node/view/79
What's so impressive? Well, let's start wth that it's a 128 bit
.. fully populating a 128-bit storage pool would, literally, require
more energy than boiling the oceans.
That pretty well covers it, I guess.
ZFS is supposed to be easier to comprehend and administer. I'm
all for that: I have often complained that filesystems like
Veritas (a former favorite of Sun) can
be very difficult. I have yet to put up a Solaris 10 box so am not
ready to agree that it is easy yet, but any improvement will be
Every bit of data is protected by a 64 bit checksum. That ought
to be impressive. The Sun folk also do a lot of talking about how
its copy-on-write design eliminates the need for fsck:
Data can be corrupted in a number of ways, such as a system error
or an unexpected power outage, but ZFS removes this fear of the
unknown. ZFS prevents data corruption by keeping data self-consistent
at all times. All operations are transactional. This not only
maintains consistency but also removes almost all of the constraints
on I/O order and allows changes to succeed or fail as a whole.
All operations are also copy-on-write. Live data is never overwritten.
ZFS writes data to a new block before changing the data pointers
and committing the write.
(from pan style="text-decoration:line-through;color:red">
http://www.sun.com/2004-0914/feature/(link dead, sorry))
Ok, so it's transaction based. That doesn't entirely eliminate
the need for fsck-like integrity checking, but it does make it
ZFS is also "self-healing":
As part of Sun's quest to build truly self-healing systems (see
the September 7 Sun.com feature), ZFS can self-heal data in a
mirrored or RAID configuration. When one copy is damaged, ZFS
detects it via the checksum and uses another copy to repair it.
No competing product can do this. Traditional mirrors can only
handle total failure of a device. They don't have checksums, so
they have no idea when a device returns bad data. So even though
mirrors replicate data, they have no way to take advantage of it.
By contrast, the end-to-end checksums in ZFS allow it to find and
fix bad blocks--with nineteen nines certainty--automatically.
Well, it's all very interesting. Snapshots, of course, and
tantalizing other things like "Multiple block sizes, automatically
chosen to match workload", which certainly would be a neat trick.
Apparently you can choose block size on a file-by-file basis.
I'll be interested to learn more about this. There are, of
course, already nay-sayers who say ZFS will be too slow. Unless it
is dog-slow, the other benefits could easily outweigh that, and we
need to remember that hardware gets faster every year. If improved
semantics for software require faster hardware, the hardware will
catch up. That's always been true.
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