[DRBD-user] Regarding Best way for snapshotting with ZFS/LVM as backing disk for drbd

[Chitvan Chhabra]

All Suggestions are most welcome.

On Fri, 29 Jul 2022 at 16:58, Chitvan Chhabra <chitvan1988 at gmail.com> wrote:

> Please suggest the Best Way to snapshot Secondary DRBD Volume(Upper) on
> LVM/ZFS(Backing) using protocol A i.e Minor Data Loss(few Seconds) is OK
> but data should remain crash consistent like Database.Also Metadata is
> external in secondary. So Do i need to snapshot external metadata as well.
> if yes Why ?
>
>
> On Above few Queries are detailed below:
>
>
> 1)As per valuable suggestions by community that normal ZFS/LVM Snapshots
> would do as long as it is upto date? How to know that in realtime uptodate
> Status as drdbadm status command doesnot appear to be realtime in nature as
> it takes time to reflect actual Status for example when primary goes down ,
> only after few seconds only it shows as connecting
>
>
> 2) Community has again suggested for internal only metadata to have
> simultaneous/atomic snapshot of both data and metadata .If the primary is
> having external metadata , it makes sense to have external metadata in
> secondary as well. But Why do we need to preserve the metadata via snapshot
> at the first place as it is believed that once you rollback the using the
> snapshot drbd would get confused and would attempt resynchronisation of the
> entire device again any way
>
>
> 3) Do i need to suspend-io first before taking the snapshot and then check
> up to date Status mandatorily ?
>
>
> 4) Last Query is regarding metadata, Does Metadata contains actual data in
> the form of Activity log/extents.Then what is drbdadm apply-al is
> for?Depending on the reply of this query we would be able to get crash
> consistent data (via backing disk snapshot clone ofcourse) even if we loose
> the metadata
>
>
> Thanks and Regards,
>
> Chitvan Chhabra
>
> +919911208768
>
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