Hard drives with 4 KB sectors and small file systems
Has anyone experience or can provide a link to information on
performance impact with the new hard drives with 4 KB sectors when
using file system with 1 KB block size?
My question is not about the alignment issue caused by
physical/logical sector size of 4096/512 Bytes. I haven't yet played
with that but I also wouldn't expect any problems here since 4 KB
alignment should be easy to achieve.
But I have a number of ext3 and ext4 file systems that use a small
block size of 1 KB. This is because of the average small file size on
these file systems, e.g. the news spool with an average file size of
2900 Bytes. Going to 4 KB block size would cause an increase of the
internal fragmentation from about 15% to approx. 42% which I wouldn't
like.
But with a 4 KB sector size and 1 KB file system block size writing of
a file might decrease performance significantly. When writing a file,
e.g. with dd if=/dev/zero of=foo bs=2900 count=1, instead of writing 3
blocks of 1 KB, i.e. 6 sectors of 512 B, it would be necessary to read
a 4 KB sector, modify 3 KB of it and write it back (assuming the 3 KB
are in the same 4 KB sector, otherwise two reads and 2 writes would be
necessary).
Has anyone practical performance figures for such a scenario?
urs
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