Hi All,
We have a XFS filesystems on Prod side and when we trying to mount the DR copy, we get superblock error
root@:~# rbd-nbd map nfs/dir
/dev/nbd0
root@:~# mount /dev/nbd0 /mnt
mount: /dev/nbd0: can't read superblock
Any suggestions to test the DR copy any other way or if I'm doing something wrong?
Thanks,
-Vikas
-----Original Message-----
From: Jason Dillaman <jdillama@xxxxxxxxxx>
Sent: Thursday, November 21, 2019 10:24 AM
To: Vikas Rana <vrana@xxxxxxxxxxxx>
Cc: dillaman <dillaman@xxxxxxxxxx>; ceph-users <ceph-users@xxxxxxxxxxxxxx>
Subject: Re: RBD Mirror DR Testing
On Thu, Nov 21, 2019 at 10:16 AM Vikas Rana <vrana@xxxxxxxxxxxx> wrote:
>
> Thanks Jason.
> We are just mounting and verifying the directory structure and make sure it looks good.
>
> My understanding was, in 12.2.10, we can't mount the DR snapshot as the RBD image is non-primary. Is this wrong?
You have always been able to access non-primary images for read-only operations (only writes are prevented):
$ rbd info test
rbd image 'test':
<... snip ...>
mirroring primary: false
$ rbd device --device-type nbd map test@1
/dev/nbd0
$ mount /dev/nbd0 /mnt/
mount: /mnt: WARNING: device write-protected, mounted read-only.
$ ll /mnt/
total 0
-rw-r--r--. 1 root root 0 Nov 21 10:20 hello.world
> Thanks,
> -Vikas
>
> -----Original Message-----
> From: Jason Dillaman <jdillama@xxxxxxxxxx>
> Sent: Thursday, November 21, 2019 9:58 AM
> To: Vikas Rana <vrana@xxxxxxxxxxxx>
> Cc: ceph-users <ceph-users@xxxxxxxxxxxxxx>
> Subject: Re: RBD Mirror DR Testing
>
> On Thu, Nov 21, 2019 at 9:56 AM Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
> >
> > On Thu, Nov 21, 2019 at 8:49 AM Vikas Rana <vrana@xxxxxxxxxxxx> wrote:
> > >
> > > Thanks Jason for such a quick response. We are on 12.2.10.
> > >
> > > Checksuming a 200TB image will take a long time.
> >
> > How would mounting an RBD image and scanning the image be faster?
> > Are you only using a small percentage of the image?
>
> ... and of course, you can mount an RBD snapshot in read-only mode.
>
> > > To test the DR copy by mounting it, these are the steps I'm
> > > planning to follow 1. Demote the Prod copy and promote the DR copy
> > > 2. Do we have to recreate the rbd mirror relationship going from DR to primary?
> > > 3. Mount and validate the data
> > > 4. Demote the DR copy and promote the Prod copy 5. Revert the peer
> > > relationship if required?
> > >
> > > Did I do it right or miss anything?
> >
> > You cannot change the peers or you will lose the relationship. If
> > you insist on your course of action, you just need to be configured
> > for two-way mirroring and leave it that way.
> >
> > >
> > > Thanks,
> > > -Vikas
> > >
> > > -----Original Message-----
> > > From: Jason Dillaman <jdillama@xxxxxxxxxx>
> > > Sent: Thursday, November 21, 2019 8:33 AM
> > > To: Vikas Rana <vrana@xxxxxxxxxxxx>
> > > Cc: ceph-users <ceph-users@xxxxxxxxxxxxxx>
> > > Subject: Re: RBD Mirror DR Testing
> > >
> > > On Thu, Nov 21, 2019 at 8:29 AM Vikas Rana <vrana@xxxxxxxxxxxx> wrote:
> > > >
> > > > Hi all,
> > > >
> > > >
> > > >
> > > > We have a 200TB RBD image which we are replicating using RBD mirroring.
> > > >
> > > > We want to test the DR copy and make sure that we have a consistent copy in case primary site is lost.
> > > >
> > > >
> > > >
> > > > We did it previously and promoted the DR copy which broken the DR copy from primary and we have to resync the whole 200TB data.
> > > >
> > > >
> > > >
> > > > Is there any correct way of doing it so we don’t have to resync all 200TB again?
> > >
> > > Yes, create a snapshot on the primary site and let it propagate to the non-primary site. Then you can compare checksums at the snapshot w/o having to worry about the data changing. Once you have finished, delete the snapshot on the primary site and it will propagate over to the non-primary site.
> > >
> > > >
> > > >
> > > > Can we demote current primary and then promote the DR copy and test and then revert back? Will that require the complete 200TB sync?
> > > >
> > >
> > > It's only the forced-promotion that causes split-brain. If you gracefully demote from site A and promote site B, and then demote site B and promote site A, that will not require a sync. However, again, it's probably just easier to use a snapshot.
> > >
> > > >
> > > > Thanks in advance for your help and suggestions.
> > > >
> > > >
> > > >
> > > > Thanks,
> > > >
> > > > -Vikas
> > > >
> > > > _______________________________________________
> > > > ceph-users mailing list
> > > > ceph-users@xxxxxxxxxxxxxx
> > > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> > >
> > >
> > >
> > > --
> > > Jason
> > >
> > >
> >
> >
> > --
> > Jason
>
>
>
> --
> Jason
>
>
--
Jason
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
