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authorNed Bass <[email protected]>2012-02-29 10:08:20 -0800
committerBrian Behlendorf <[email protected]>2012-03-05 09:49:50 -0800
commit613d88eda89945bb0011ddc05d3bd064bf1a8e1b (patch)
tree15d24445dc675b198b50e47800e49c803264598d /COPYRIGHT
parentec2626ad3f695a2ced3946c4197ef64cbcac4959 (diff)
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 <[email protected]> Closes #574
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