Re: Low level bluestore usage

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On 23/09/2020 04:09, Alexander E. Patrakov wrote:

Sometimes this doesn't help. For data recovery purposes, the most
helpful step if you get the "bluefs enospc" error is to add a separate
db device, like this:

systemctl disable --now ceph-osd@${OSDID}
truncate -s 32G /junk/osd.${OSDID}-recover/block.db
sgdisk -n 0:0:0 /junk/osd.${OSDID}-recover/block.db
ceph-bluestore-tool \
     bluefs-bdev-new-db --path /var/lib/ceph/osd/ceph-${OSDID} \
     --dev-target /junk/osd.${OSDID}-recover/block.db \
     --bluestore-block-db-size=31G --bluefs-log-compact-min-size=31G

Of course you can use a real block device instead of just a file.

After that, export all PGs using ceph-objecttstore-tool and re-import
into a fresh OSD, then destroy or purge the full one.

Here is why the options:

--bluestore-block-db-size=31G: ceph-bluestore-tool refuses to do
anything if this option is not set to any value
--bluefs-log-compact-min-size=31G: make absolutely sure that log
compaction doesn't happen, because it would hit "bluefs enospc" again.


Oh, you went this way... I solved my 'pocket ceph' needs by exporting disk images (from files) via iscsi and mounting them back to localhost. That gives me a perfect 'scsi' devices which work exactly as in production. I have a little playbook (iscsi_loopback) to setup it on random scrap (including VMs) for development purposes. After iscsi is loopback-mounted, all other code works exactly the same as it would in production.

I've got this issue few times on small 10GB osds, so I moved to 15Gb and it become a less often. I never have had this in real-hardware tests with real disk sizes (>>100G per OSD).
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