On Fri, Jul 22, 2011 at 01:05:14PM -0500, Stan Hoeppner wrote:
> On 7/22/2011 1:10 AM, Michael Monnerie wrote:
> > Yes, I just wanted to know about the corner cases, and how XFS behaves.
> > Actually, we're changing over to using NetApps, and with their WAFL
> > anyway I should drop all su/sw usage and just use 4KB blocks.
> I've never used a NetApp filer myself. However, that said, I would
> assume that WAFL is only in play for NFS/CIFS transactions since WAFL is
> itself a filesystem.
Netapp's website is busted, so here's a cached link:
"The point is that WAFL is the part of the code that provides the
'read or write from-disk' mechanisms to both NFS and CIFS and SAN.
The semantics of a how the blocks are accessed are provided by
higher level code not by WAFL, which means WAFL is not a file
If you can be bothered trolling for that entire series of blog posts
in the google cache, it's probably a good idea so you can get a
basic understanding of what WAFL actually is.
> When exposing LUNs from the same filer to FC and iSCSI hosts I would
> assume the filer acts just as any other SAN controller would.
It has it's own quirks, just like any other FC attached RAID array...
> In this case I would think you'd probably still want to align your
> XFS filesystem to the underlying RAID stripe from which the LUN
> was carved.
Which actually matters very little when WAFL between the FS and the
disk because WAFL uses copy-on-write and stages all it's writes
through NVRAM and so you've got no idea what the alignment of any
given address in the filesystem maps to, anyway.