If you use ceph-disk (and I believe ceph-depoly) to create your OSDs, or you go through the manual steps to set up the partition UUIDs, then yes udev and the init script will do all the magic. Your disks can be moved to another box without problems. I've moved disks to different ports on controllers and it all worked just fine. I will be swapping the disks between two boxes today to try to get to the bottom of some problems we have been having, if it doesn't work I'll let you know.
The automagic of ceph OSDS has been refreshing for me because I was worried about having to manage so many disks and mount points, but it is much easier than I anticipated once I used ceph-disk.
Robert LeBlanc
Sent from a mobile device please excuse any typos.
On May 11, 2015 5:32 AM, "Georgios Dimitrakakis" <giorgis@xxxxxxxxxxxx> wrote:
Hi Robert,
just to make sure I got it correctly:
Do you mean that the /etc/mtab entries are completely ignored and no matter what the order
of the /dev/sdX device is Ceph will just mount correctly the osd/ceph-X by default?
In addition, assuming that an OSD node fails for a reason other than a disk problem (e.g. mobo/ram)
if I put its disks on another OSD node (all disks have their journals with) will Ceph be able to mount
them correctly and continue its operation?
Regards,
George
I have not used ceph-deploy, but it should use ceph-disk for the OSD_______________________________________________
preparation. Ceph-disk creates GPT partitions with specific
partition UUIDS for data and journals. When udev or init starts the
OSD, or mounts it to a temp location reads the whoami file and the
journal, then remounts it in the correct location. There is no need
for fstab entries or the like. This allows you to easily move OSD
disks between servers (if you take the journals with it). Its magic!
But I think I just gave away the secret.
Robert LeBlanc
Sent from a mobile device please excuse any typos.
On May 7, 2015 5:16 AM, "Georgios Dimitrakakis" wrote:
Indeed it is not necessary to have any OSD entries in the Ceph.conf
file
but what happens in the event of a disk failure resulting in
changing the mount device?
For what I can see is that OSDs are mounted from entries in
/etc/mtab (I am on CentOS 6.6)
like this:
/dev/sdj1 /var/lib/ceph/osd/ceph-8 xfs rw,noatime,inode64 0 0
/dev/sdh1 /var/lib/ceph/osd/ceph-6 xfs rw,noatime,inode64 0 0
/dev/sdg1 /var/lib/ceph/osd/ceph-5 xfs rw,noatime,inode64 0 0
/dev/sde1 /var/lib/ceph/osd/ceph-3 xfs rw,noatime,inode64 0 0
/dev/sdi1 /var/lib/ceph/osd/ceph-7 xfs rw,noatime,inode64 0 0
/dev/sdf1 /var/lib/ceph/osd/ceph-4 xfs rw,noatime,inode64 0 0
/dev/sdd1 /var/lib/ceph/osd/ceph-2 xfs rw,noatime,inode64 0 0
/dev/sdk1 /var/lib/ceph/osd/ceph-9 xfs rw,noatime,inode64 0 0
/dev/sdb1 /var/lib/ceph/osd/ceph-0 xfs rw,noatime,inode64 0 0
/dev/sdc1 /var/lib/ceph/osd/ceph-1 xfs rw,noatime,inode64 0 0
So in the event of a disk failure (e.g. disk SDH fails) then in the
order the next one will take its place meaning that
SDI will be seen as SDH upon next reboot thus it will be mounted as
CEPH-6 instead of CEPH-7 and so on...resulting in a problematic
configuration (I guess that lots of data will be start moving
around, PGs will be misplaced etc.)
Correct me if I am wrong but the proper way to mount them would be
by using the UUID of the partition.
Is it OK if I change the entries in /etc/mtab using the UUID=xxxxxx
instead of /dev/sdX1??
Does CEPH try to mount them using a different config file and
perhaps exports the entries at boot in /etc/mtab (in the latter case
no modification in /etc/mtab will be taken into account)??
I have deployed the Ceph cluster using only the "ceph-deploy"
command. Is there a parameter that I ve missed that must be used
during deployment in order to specify the mount points using the
UUIDs instead of the device names?
Regards,
George
On Wed, 6 May 2015 22:36:14 -0600, Robert LeBlanc wrote:
We dont have OSD entries in our Ceph config. They are not needed
if
you dont have specific configs for different OSDs.
Robert LeBlanc
Sent from a mobile device please excuse any typos.
On May 6, 2015 7:18 PM, "Florent MONTHEL" wrote:
Hi teqm,
Is it necessary to indicate in ceph.conf all OSD that we have
in the
cluster ?
we have today reboot a cluster (5 nodes RHEL 6.5) and some OSD
seem
to have change ID so crush map not mapped with the reality
Thanks
FLORENT MONTHEL
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