freebsd-dev/module
Brian Behlendorf 2959d94a0a Add FAILFAST support
ZFS works best when it is notified as soon as possible when a device
failure occurs.  This allows it to immediately start any recovery
actions which may be needed.  In theory Linux supports a flag which
can be set on bio's called FAILFAST which provides this quick
notification by disabling the retry logic in the lower scsi layers.

That's the theory at least.  In practice is turns out that while the
flag exists you oddly have to set it with the BIO_RW_AHEAD flag.
And even when it's set it you may get retries in the low level
drivers decides that's the right behavior, or if you don't get the
right error codes reported to the scsi midlayer.

Unfortunately, without additional kernels patchs there's not much
which can be done to improve this.  Basically, this just means that
it may take 2-3 minutes before a ZFS is notified properly that a
device has failed.  This can be improved and I suspect I'll be
submitting patches upstream to handle this.
2010-10-12 14:55:02 -07:00
..
avl Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
nvpair Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
unicode Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zcommon Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zfs Add FAILFAST support 2010-10-12 14:55:02 -07:00
zpios Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
.gitignore Add .gitignore files to exclude build products 2010-01-08 11:35:17 -08:00
Makefile.in Support custom build directories and move includes 2010-09-08 12:38:56 -07:00