zfs/lib
Ned Bass 613d88eda8 Align parition end on 1 MiB boundary
Some devices have exhibited sensitivity to the ending alignment of
partitions.  In particular, even if the first partition begins at 1
MiB, we have seen many sd driver task abort errors with certain SSDs
if the first partition doesn't end on a 1 MiB boundary.  This occurs
when the vdev label is read during pool creation or importation and
causes a delay of about 30 seconds per device.  It can also be
simulated with dd when the pool isn't imported:

  dd if=/dev/sda1 of=/dev/null bs=262144 count=1

For the record, this problem was observed with SMARTMOD
SG9XCA2E200GE01 200GB SSDs.  Unfortunately I don't have a good
explanation for this behavior. It seems to have something to do with
highly fragmented single-sector requests being issued to the device,
which it may not support.  With end-aligned partitions at least
page-sized requests were queued and issued to the driver according
to blktrace. In any case, aligning the partition end is a fairly
innocuous work-around, wasting at most 1 MiB of space.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #574
2012-03-05 09:49:50 -08:00
..
libavl Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libefi Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libnvpair Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libshare Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libspl Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libunicode Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libuutil Cleanly support debug packages 2012-02-27 14:08:17 -08:00
libzfs Align parition end on 1 MiB boundary 2012-03-05 09:49:50 -08:00
libzpool Cleanly support debug packages 2012-02-27 14:08:17 -08:00
Makefile.am Let libnvpair be linked independently of libzfs. 2012-02-07 11:37:15 -08:00
Makefile.in Cleanly support debug packages 2012-02-27 14:08:17 -08:00