[ceph-users] size of inc_osdmap vs osdmap

[Sergey Dolgov]

Hi guys

I faced strange behavior of crushmap change. When I change crush
weight osd I sometimes get increment osdmap(1.2MB) which size is
significantly bigger than size of osdmap(0.4MB)
I use luminois 12.2.8. Cluster was installed a long ago, I suppose
that initially it was firefly
How can I view content of increment osdmap or can you give me opinion
on this problem. I think that spikes of traffic tight after change of
crushmap relates to this crushmap behavior

[Gregory Farnum]

Post by Sergey Dolgov
Hi guys
I faced strange behavior of crushmap change. When I change crush
weight osd I sometimes get increment osdmap(1.2MB) which size is
significantly bigger than size of osdmap(0.4MB)

This is probably because when CRUSH changes, the new primary OSDs for a PG
will tend to set a "pg temp" value (in the OSDMap) that temporarily
reassigns it to the old acting set, so the data can be accessed while the
new OSDs get backfilled. Depending on the size of your cluster, the number
of PGs on it, and the size of the CRUSH change, this can easily be larger
than the rest of the map because it is data with size linear in the number
of PGs affected, instead of being more normally proportional to the number
of OSDs.
-Greg

Post by Sergey Dolgov
I use luminois 12.2.8. Cluster was installed a long ago, I suppose
that initially it was firefly
How can I view content of increment osdmap or can you give me opinion
on this problem. I think that spikes of traffic tight after change of
crushmap relates to this crushmap behavior
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