Andrzej Butkiewicz wrote:
Thanks Mark!
I see that writing part of filesystem block reduces performance. Especially in
Raid-Z because we have to read all spread on every disk blocks. Does ZFS have
any kind of blocks aggregation?
I suppose that could be work on this way: zfs receive a command to write part
of the block, e.g. last 8kB in 32kB block. Next, instead that read-modify-write
we write modify information into the cache and wait for next modification of
this block. If any next write-command will fill all parts of the block we will
could write whole block without reading it.
Why I'm asking? I'm very interesting in which implementations Raid-Z will have
better
performance than Raid-5. And which way I must improve my applications to obtain
better
performance with ZFS? (constant writing blocks??)
If performance is really this critical to you Raid-Z is probably not the
correct choice.
Can you actually prove that this aspect of ZFS is actually causing a
performance problem for you or are you making assumptions ?
--
Darren J Moffat
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