diff options
| author | Brian Behlendorf <[email protected]> | 2010-10-01 10:57:56 -0700 |
|---|---|---|
| committer | Brian Behlendorf <[email protected]> | 2010-10-12 14:55:02 -0700 |
| commit | 2959d94a0a53612cc1ca9ce9d17df26c3d69a513 (patch) | |
| tree | f4571ef38043563b698daa65e0db62e69de46868 /config/kernel-bio-failfast.m4 | |
| parent | c5343ba71b9fea6e3636be25a16173092f2042ba (diff) | |
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.
Diffstat (limited to 'config/kernel-bio-failfast.m4')
| -rw-r--r-- | config/kernel-bio-failfast.m4 | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/config/kernel-bio-failfast.m4 b/config/kernel-bio-failfast.m4 new file mode 100644 index 000000000..acc657562 --- /dev/null +++ b/config/kernel-bio-failfast.m4 @@ -0,0 +1,22 @@ +dnl # +dnl # 2.6.28 API change +dnl # Device, transport, and driver FAILFAST flags were added and +dnl # the now legacy BIO_RW_FAILFAST flag was removed. +dnl # +AC_DEFUN([ZFS_AC_KERNEL_BIO_FAILFAST], [ + AC_MSG_CHECKING([whether BIO_RW_FAILFAST_* are defined]) + ZFS_LINUX_TRY_COMPILE([ + #include <linux/bio.h> + ],[ + int flags; + flags = ((1 << BIO_RW_FAILFAST_DEV) | + (1 << BIO_RW_FAILFAST_TRANSPORT) | + (1 << BIO_RW_FAILFAST_DRIVER)); + ],[ + AC_MSG_RESULT(yes) + AC_DEFINE(HAVE_BIO_RW_FAILFAST, 1, + [BIO_RW_FAILFAST_* are defined]) + ],[ + AC_MSG_RESULT(no) + ]) +]) |