On 24.09.2015 19:03, Sage Weil wrote:
On Thu, 24 Sep 2015, Igor Fedotov wrote:
Dynamic stripe sizes are possible but it's a significant change from
the way the EC pool currently works. I would make that a separate
project (as its useful in its own right) and not complicate the
compression situation. Or, if it simplifies the compression approach,
then I'd make that change first. sage
Just to clarify a bit. What I saw when played with Ceph. Please correct
me if I'm wrong..
For low-level RADOS access client data written to EC pool has to be
aligned with stripe size . The last block can be unaligned though but no
more appends are permitted in this case.
Data copied from cache goes in blocks up to 8Mb size. In general case
the last block seems to have unaligned size too.
EC pool additionally performs alignment of the incoming blocks to stripe
bound internally. This way blocks going to EC lib are always aligned.
We should probably perform compression prior to this alignment.
Thus some dependency on stripe size is present in EC pools but it's not
that strict.
Thanks,
Igor
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