On Tue, Jun 03, 2008 at 09:37:27AM -0500, Thomas King wrote:

quoted

All the issues he complains about actually are solved by XFS, and XFS actually

does better in

quoted

exactly these environments than either zfs on Solaris or JFS2 on AIX.

I asked the author that question and he states XFS is actually a pretty good
answer to most of those issues but believes it still falls short where "the
metadata areas are not aligned with RAID strips and allocation units are FAR too
small but better than ext."

I think it would be best to let the XFS developers answer this part.
But, XFS is designed for and used in massive installations, and I think
it represents a scalability goal for Btrfs.

Another detail he brought out was sending data and
metadata to different devices in those environments and referenced RT XFS.
Otherwise having them on the same device increases the possibility of corruption
and/or a longer filesystem check/repair. Will btrfs offer something like this in
the future?

Btrfs can duplicate metadata via the internal raid1 and raid10 code.  On
single spindles it will duplicate metadata as well.  This is different
from RT XFS which I do not understand well.

There is not code today in btrfs to force data and metadata to different
devices, but the disk format has the bits it needs to make that happen.
I think it is an oversimplification to say that splitting the two
between devices changes the chances of a corruption, or changes the time
a repair takes.

Btrfs does split data and metadata allocations, grouping metadata
together in large chunks on the drive.  This does make FS check/repair
faster by reducing seeks between metadata blocks.

Do y'all foresee btrfs being used in exabtye installations?

Yes

Does/Will btrfs have RAID awareness in that it will align "the
superblock and metadata to the RAID stripe"?

Today the superblock is not stripe aligned, but it will be in a future
release that supports super block duplication.  At least, the
blocks that are frequently written will be striped aligned.

What is the largest block allocation available?

2^64 bytes.  But, in COW filesystems massive extents have different
costs than they do in traditional filesystems.  It isn't always a good
idea to make a huge extent.

Will btrfs be T10 DIF/block protect aware?

I work closely with Martin, and we'll leverage the T10 DIF code as much
as possible.

I remember reading that CRFS relies on btrfs, but will btrfs support NFS,
specifically version 4.1?

We'll definitely support NFS.  It doesn't work today, but it will before
1.0.

-chris