[ceph-users] Filestore to Bluestore migration question

Hayashida, Mami mami.hayashida at uky.edu
Wed Oct 31 05:27:25 PDT 2018


Thank you for your replies. So, if I use the method Hector suggested (by
creating PVs, VGs.... etc. first), can I add the --osd-id parameter to the
command as in

ceph-volume lvm prepare --bluestore --data hdd0/data0 --block.db ssd/db0
--osd-id 0
ceph-volume lvm prepare --bluestore --data hdd1/data1 --block.db ssd/db1
--osd-id 1

so that Filestore -> Bluestore migration will not change the osd ID on each
disk?

And one more question.  Are there any changes I need to make to the
ceph.conf file?  I did comment out this line that was probably used for
creating Filestore (using ceph-deploy):  osd journal size = 40960



On Wed, Oct 31, 2018 at 7:03 AM, Alfredo Deza <adeza at redhat.com> wrote:

> On Wed, Oct 31, 2018 at 5:22 AM Hector Martin <hector at marcansoft.com>
> wrote:
> >
> > On 31/10/2018 05:55, Hayashida, Mami wrote:
> > > I am relatively new to Ceph and need some advice on Bluestore
> migration.
> > > I tried migrating a few of our test cluster nodes from Filestore to
> > > Bluestore by following this
> > > (http://docs.ceph.com/docs/luminous/rados/operations/bluesto
> re-migration/)
> > > as the cluster is currently running 12.2.9. The cluster, originally set
> > > up by my predecessors, was running Jewel until I upgraded it recently
> to
> > > Luminous.
> > >
> > > OSDs in each OSD host is set up in such a way that for ever 10 data HDD
> > > disks, there is one SSD drive that is holding their journals.  For
> > > example, osd.0 data is on /dev/sdh and its Filestore journal is on a
> > > partitioned part of /dev/sda. So, lsblk shows something like
> > >
> > > sda       8:0    0 447.1G  0 disk
> > > ├─sda1    8:1    0    40G  0 part # journal for osd.0
> > >
> > > sdh       8:112  0   3.7T  0 disk
> > > └─sdh1    8:113  0   3.7T  0 part /var/lib/ceph/osd/ceph-0
> > >
> >
> > The BlueStore documentation states that the wal will automatically use
> > the db volume if it fits, so if you're using a single SSD I think
> > there's no good reason to split out the wal, if I'm understanding it
> > correctly.
>
> This is correct, no need for wal in this case.
>
> >
> > You should be using ceph-volume, since ceph-disk is deprecated. If
> > you're sharing the SSD as wal/db for a bunch of OSDs, I think you're
> > going to have to create the LVs yourself first. The data HDDs should be
> > PVs (I don't think it matters if they're partitions or whole disk PVs as
> > long as LVM discovers them) each part of a separate VG (e.g. hdd0-hdd9)
> > containing a single LV. Then the SSD should itself be an LV for a
> > separate shared SSD VG (e.g. ssd).
> >
> > So something like (assuming sda is your wal SSD and sdb and onwards are
> > your OSD HDDs):
> > pvcreate /dev/sda
> > pvcreate /dev/sdb
> > pvcreate /dev/sdc
> > ...
> >
> > vgcreate ssd /dev/sda
> > vgcreate hdd0 /dev/sdb
> > vgcreate hdd1 /dev/sdc
> > ...
> >
> > lvcreate -L 40G -n db0 ssd
> > lvcreate -L 40G -n db1 ssd
> > ...
> >
> > lvcreate -L 100%VG -n data0 hdd0
> > lvcreate -L 100%VG -n data1 hdd1
> > ...
> >
> > ceph-volume lvm prepare --bluestore --data hdd0/data0 --block.db ssd/db0
> > ceph-volume lvm prepare --bluestore --data hdd1/data1 --block.db ssd/db1
> > ...
> >
> > ceph-volume lvm activate --all
> >
> > I think it might be possible to just let ceph-volume create the PV/VG/LV
> > for the data disks and only manually create the DB LVs, but it shouldn't
> > hurt to do it on your own and just give ready-made LVs to ceph-volume
> > for everything.
>
> Another alternative here is to use the new `lvm batch` subcommand to
> do all of this in one go:
>
> ceph-volume lvm batch /dev/sda /dev/sdb /dev/sdc /dev/sdd /dev/sde
> /dev/sdf /dev/sdg /dev/sdh
>
> Will detect that sda is an SSD and will create the LVs for you for
> block.db (one for each spinning disk). For each spinning disk, it will
> place data on them.
>
> The one caveat is that you no longer control OSD IDs, and they are
> created with whatever the monitors are giving out.
>
> This operation is not supported from ceph-deploy either.
> >
> > --
> > Hector Martin (hector at marcansoft.com)
> > Public Key: https://marcan.st/marcan.asc
> > _______________________________________________
> > ceph-users mailing list
> > ceph-users at lists.ceph.com
> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>



-- 
*Mami Hayashida*

*Research Computing Associate*
Research Computing Infrastructure
University of Kentucky Information Technology Services
301 Rose Street | 102 James F. Hardymon Building
Lexington, KY 40506-0495
mami.hayashida at uky.edu
(859)323-7521
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