KB450403 – Adding SSD Journals to OSDs

Last modified: May 27, 2021
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Scope/Description:

This article will go through the steps required to add journals from SSDs to your OSDs (HDD)

Prerequisites:

  • Stable ceph cluster
  • OSDs on Hard Drives
  • SSDs added to the each OSD node within the cluster

Steps:

CREATE LVM DEVICES ON SSD

pvcreate /dev/1-6

vgcreate ceph-db-0 /dev/1-6

lvcreate -l <extents> -n osd-db-0 ceph-db-0

extents = # of 4MiB blocks

extents = 7680 = 30GiB

 

ASSIGN PERMISSIONS

chown -h ceph:ceph /dev/ceph-0/osd-db-0

chown -R ceph:ceph $(realpath /dev/ceph-0/osd-db-0)

 

 

STOP OSD

ceph osd set noout

systemctl stop ceph-osd@2

 

CREATE NEW block.db DEVICE

CEPH_ARGS=”–bluestore-block-db-size 32212254720″ ceph-bluestore-tool bluefs-bdev-new-db –path /var/lib/ceph/osd/ceph-2/ –dev-target /dev/ceph-db-0/osd-db-0

 

MIGRATE EXISTING BLOCK.DB DATA TO NEW DEVICE

ceph-bluestore-tool –path /var/lib/ceph/osd/ceph-2/ –devs-source /var/lib/ceph/osd/ceph-2/block –dev-target /var/lib/ceph/osd/ceph-2/block.db bluefs-bdev-migrate

 

 

CREATE LVM TAGS ON NEW BLOCK.DB AND EXISTING BLOCK

./add-lv-tags /dev/ceph-a493b896-e6e0-449f-9b06-c2daeb69cb92/osd-block-47b0a1d9-43e6-4ffe-925b-855548699a0b /dev/ceph-0/osd-db-0

 

 

UMOUNT OSD DIR AND RUN CEPH-VOLUME ACTIVATE

umount /var/lib/ceph/osd-2/

ceph-volume lvm activate –all

 

 

START OSD & UNSET NOOUT 

systemctl start ceph-osd@2

ceph osd unset noout

Verification:

Run “ceph-volume lvm list” and find the OSD you just did to confirm it now reports having a [DB] device attached to it.

 

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