Re: Odd behaviour of two identical ZFS servers mirroring via rsync

From: Mehmet Erol Sanliturk <m.e.sanliturk_at_gmail.com>
Date: Sun, 13 Nov 2022 19:03:15 UTC 
On Sun, Nov 13, 2022 at 8:46 PM Bob Friesenhahn <
bfriesen@simple.dallas.tx.us> wrote:

> On Sun, 13 Nov 2022, Mark Saad wrote:
> >>
> > Bob are you saying when the target is zfs --inplace --no-whole-file helps
> > or just in general when you have
> > large files ?  Also have you tried using --delete-during /
> --delete-after  ?
>
> The '-inplace --no-whole-file' updates the file blocks if they have
> changed (comparing the orgin blocks with the existing mirror blocks)
> rather than creating a new copy of the file and moving it into place
> when it is complete.  ZFS does not check if data content has been
> changed while it is being written so a write of the same data will
> result in a fresh allocation based on its Copy On Write ("COW")
> design.  Writing a whole new file obviously significantly increases
> the number of blocks which are written.  Requesting that rsync only
> write to the file for the blocks which have changed reduces the total
> number of blocks which get written.
>
> The above helps quite a lot when using snapshots since then fewer
> blocks are in the snapshots.
>
> I have never tried --delete-during so I can't comment on that.
>
> Bob
> --
> Bob Friesenhahn
> bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
> Public Key,     http://www.simplesystems.org/users/bfriesen/public-key.txt
>
>


More information on zfs and rsync :


https://www.google.com/search?q=use+of+rsync+command+for+zfs+volumes&sxsrf=ALiCzsZALxJWD--EizNVNAHl-u-j6BOndw%3A1668365903483&source=hp&ei=Tz5xY6XbGrCQxc8Plbyl8A0&iflsig=AJiK0e8AAAAAY3FMX56shwXahupzkNcfFLLhJJd0xL1U&ved=0ahUKEwjlvp6o66v7AhUwSPEDHRVeCd4Q4dUDCAc&uact=5&oq=use+of+rsync+command+for+zfs+volumes&gs_lcp=Cgdnd3Mtd2l6EAMyBQgAEKIEOgQIIxAnOgsILhCABBDHARDRAzoFCAAQgAQ6CAguENQCEIAEOggILhCABBDUAjoFCC4QgAQ6CAgAEIAEEMsBOggILhCABBDLAToGCAAQFhAeOggIABAWEB4QDzoFCAAQhgM6BQghEKABOgQIIRAVOggIIRAWEB4QHToHCCEQoAEQClAAWI6bAmCtnQJoAHAAeACAAbkCiAHkLJIBCDAuMzUuMC4xmAEAoAEB&sclient=gws-wiz

use of rsync command for zfs volumes



Mehmet Erol Sanliturk