ZFS, XFS, and EXT4 compared

I have a lot of people whispering "zfs" in my virtual ear these days,
and at the same time I have an irrational attachment to xfs based
entirely on its lack of the 32000 subdirectory limit.  I'm not afraid of
ext4's newness, since really a lot of that stuff has been in Lustre for
years.  So a-benchmarking I went.  Results at the bottom:

http://tastic.brillig.org/~jwb/zfs-xfs-ext4.html

Short version: ext4 is awesome.  zfs has absurdly fast metadata
operations but falls apart on sequential transfer.  xfs has great
sequential transfer but really bad metadata ops, like 3 minutes to tar
up the kernel.

It would be nice if mke2fs would copy xfs's code for optimal layout on a
software raid.  The mkfs defaults and the mdadm defaults interact badly.

Postmark is somewhat bogus benchmark with some obvious quantization
problems.

Regards,
jwb