[DRBD-user] Any way to jump over initial sync ?

[David Bruzos]

Hi Lars,
Thank you and the others for such a wonderful and useful system!  Now, to your comment:

>Um, well, while it may be "your proven method" as well, it actually is the method documented in the drbdsetup man page and the User's Guide.
    By "proven method", I ment that I've done it that way hundreds of times and never had a problem, but I'm not sure if it is the only way...
    Yeah, I'm sure that is where I got it from a couple of years ago (I always read the excellent DRBD docs before searching the WWW).
>What did you think where the guys you copied it from found it?
    Didn't think anything as I probably got it right from the docs.  :)


-- 
David Bruzos (Systems Administrator)
Jacksonville Port Authority
2831 Talleyrand Ave.
Jacksonville, FL  32206
Cell: (904) 625-0969
Office: (904) 357-3069
Email: david.bruzos at jaxport.com

On Wed, Aug 29, 2018 at 05:34:00PM +0200, Lars Ellenberg wrote:
> On Wed, Aug 29, 2018 at 08:32:27AM -0400, David Bruzos wrote:
> 
> > * Typical way to skip the sync (at least this is my proven method):
> 
> Um, well, while it may be "your proven method" as well,
> it actually is the method documented
> in the drbdsetup man page and the User's Guide.
> What did you think where the guys you copied it from found it?
> 
> >     # drbdadm create-md <resource>  -  (do this on both nodes)
> >     # drbdadm up <resource>  -  (do this on both nodes)
> >     # drbdadm -- --clear-bitmap new-current-uuid <resource>  -  (do this on secondary node)
> >     # drbdadm primary <resource>  -  (do this on primary node)
> 
> The last two steps can be done on any node,
> even on the same node.
> Obviously, after "primary", that node will be Primary.
> 
> Don't forget to now do "mkfs"
> or otherwise initilize the content of this DRBD volume.
> 
> >     # cat /proc/drbd  -  (Enjoy!)
> 
> Additional notes:
> 
> If you happen to have "huge" volumes,
> and pre-existing data (so you must not skip the initial resync,
> which would also skip replication of all the pre-existing data),
> and you use a "fstrim" capable file system that is only partially used,
> (and sufficiently recent kernel and DRBD),
> you can speed up the initial resync by promoting and mounting the
> pre-existing data, then fstrim on the mount point.
> 
> For "progress reports" during that fstrim,
> you may want to look into fstrim options -v -o -l -m ...
> 
> If you are faced with "huge" amounts of pre-existing data
> and an "unsatisfactory" replication link bandwidth,
> you may want to look into the second typical use case of
> "new-current-uuid", which we coined "truck based replication",
> which is also documented in the drbdsetup man page.
> (Or, do the initial sync with an "on-site" secondary,
> then ship that secondary, or its disk(s) to the remote site).
> 
> Cheers,
> 
> -- 
> : Lars Ellenberg
> : LINBIT | Keeping the Digital World Running
> : DRBD -- Heartbeat -- Corosync -- Pacemaker
> 
> DRBD? and LINBIT? are registered trademarks of LINBIT
> __
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