On 5/25/23 18:17, Igor Fedotov wrote:
Perhaps...
I don't like the idea to use fragmentation score as a real index. IMO
it's mostly like a very imprecise first turn marker to alert that
something might be wrong. But not a real quantitative high-quality
estimate.
Chiming in on the high fragmentation issue. We started collecting
"fragmentation_rating" of each OSD this afternoon. All OSDs that have
been provisioned a year ago have a fragmentation rating of ~ 0.9. Not
sure for how long they are on this level. And after reading your mails
it might not be a problem at all. But we will start collecting this
information in the coming weeks.
We will be re-provisioning all our OSDs, so that might be a good time to
look at the behavior and development of "cnt versus frags" ratio.
After we completely emptied a host, even after having the OSDs run idle
for a couple of hours, the fragmentation ratio would not drop lower than
0.27 for some OSDs, and up to 0.62 for others. Is it expected that this
will not go to ~ zero?
We have not noticed any performance degradation whatsoever. We are
running with bitmap for current OSDs, hybrid allocator for the new
provisioned OSDs (4k min alloc size).
Gr. Stefan
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