Hi Wesley,
during spillover (or more precisely - during "no DB space" condition, DB
spillovers tend to occur before) WAL allocations follow the same logic
as DB ones - they are served from the main device. So WAL effectively
keeps being in use but it allocates space from "slow" device.
Thanks,
Igor
On 06.01.2025 19:46, Wesley Dillingham wrote:
I have a question for bluestore experts about the ability for an OSD to
continue to make use of the WAL during spillover events when the WAL and DB
were implicitly collocated as described here:
https://docs.ceph.com/en/reef/rados/configuration/bluestore-config-ref/#devices
" whenever a DB device is specified but an explicit WAL device is not, the
WAL will be implicitly colocated with the DB on the faster device."
During DB spillover (happen because fast device's LV is out of space) does
the WAL have some guaranteed allocation of space in the LV / assurance that
it can use a fixed amount of space when in contention with the db or does
the bluestore-OSD no longer have the ability to use the WAL during
spillover?
I understand an admin could implement some workarounds to logically isolate
and protect a wal and db on the same physical media but I am curious if
such a mechanism exists already in the bluestore OSD itself. Thanks for
the clarification.
Respectfully,
*Wes Dillingham*
LinkedIn <http://www.linkedin.com/in/wesleydillingham>
wes@xxxxxxxxxxxxxxxxx
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