Re: OSDs too slow to start

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How long is “too long”? 800MB on an SSD should only be a second or three.
I’m not sure if that’s a reasonable amount of data; you could try compacting the rocksdb instance etc. But if reading 800MB is noticeable I would start wondering about the quality of your disks as a journal or rocksdb device.
-Greg

On Tue, Jun 12, 2018 at 2:23 PM Alfredo Daniel Rezinovsky <alfredo.rezinovsky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I migrated my OSDs from filestore to bluestore.

Each node now has 1 SSD with the OS and the BlockDBs and 3 HDDs with
bluestore data.

# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sdd      8:48   0   2.7T  0 disk
|-sdd2   8:50   0   2.7T  0 part
`-sdd1   8:49   0   100M  0 part /var/lib/ceph/osd/ceph-2
sdb      8:16   0   3.7T  0 disk
|-sdb2   8:18   0   3.7T  0 part
`-sdb1   8:17   0   100M  0 part /var/lib/ceph/osd/ceph-0
sdc      8:32   0   3.7T  0 disk
|-sdc2   8:34   0   3.7T  0 part
`-sdc1   8:33   0   100M  0 part /var/lib/ceph/osd/ceph-1
sda      8:0    0 223.6G  0 disk
|-sda4   8:4    0     1G  0 part
|-sda2   8:2    0  37.3G  0 part /
|-sda5   8:5    0     1G  0 part
|-sda3   8:3    0     1G  0 part
`-sda1   8:1    0   953M  0 part /boot/efi

Now the I/O works better, and I never saw again a slow response (OSD not
MDS) warning.

But when I reboot a ceph node the OSDs takes too long to get up. With
filestore it was almost inmediate.

Monitoring /proc/$(pidod ceph-osd)/io I could see that each OSD reads
about 800 MBytes before getting up (My block.db partitions are 1G).

Does the OSDs start re-process all the block.db when booting up?

There's any way to accelerate the OSD availability after a reboot?


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