[DRBD-user] Any way to jump over initial sync ?
julien.escario at altinea.fr
Wed Aug 29 17:03:21 CEST 2018
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Many many thanks for the detailled procedure.
I'll try in a few days with drbd9 and will let you know if something has to be
changed (mainly because resources are created on the fly on each side).
Le 29/08/2018 à 14:32, David Bruzos a écrit :
> Hi, I have lots of experience skipping the initial sync with ZFS zvols and
> drbd 8.4.x. I have been using the "drbdadm -- --clear-bitmap
> new-current-uuid <RESOURCE>" for years and never had a problem. This is
> why it works:
> 1. New ZFS volumes are guaranteed to return only zero data for unwritten
> blocks, so two new volumes are always in sync, if they have not been
> written to. 2. Also, if you have a VM base image on two hosts, you can
> clone the volumes in the image on each host and also skip the initial
> sync, because both clones will be identical. Of course, I am asuming that
> the base image was replicated via ZFS streams. 3. LVM volumes and most
> other volume types will not work well, because they don't guarantee new
> volumes to be zero-filled. However, depending on your use case, it is
> often better to zero-fill your volumes manually (E.G. cat /dev/zero
> >/dev/vg/vol0) and skip the sync. It does not seem reasonable, but given
> the storage and network characteristics at play, it could be much much
> better than doing an actual DRBD sync. 4. If in doubt, run a drbd verify
> until you feel confidence in your process.
> * Typical way to skip the sync (at least this is my proven method):
> # 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) # cat /proc/drbd -
> In my opinion, having to replicate multi-tb volumes is an incredible waste
> of time and resources, if it can be safely avoided. I've talked to many
> people that patiently wait while their giant 4 TB VM volumes do their
> initial sync and hog their environment's I/O in the process...
> I hope this helps you and others out there who are looking for a better
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