Re: [BackupPC-users] Windows/Linux speed differences (windows is faster?)

[Craig B. <cba...@us...>]

Cameron Dale writes:

> I'm backing up several different machines on my local network to my
> debian-based server using BackupPC. I'm using rsyncd for all of this,
> 2.6.8 on the Linux machines, and cygwin-rsyncd-2.6.2_0.zip on the
> Windows machines. One of the machines is even dual booted, and the
> same data is backed up sometimes by Windows, sometimes by Linux.
>=20
> I'm seeing differences in the speed and number of files transferred
> for incremental backups on Linux compared to Windows. Looking at the
> XferLog files, it seems that the Windows machines are only
> transferring the changed files (the log contains "create d" for all
> the directories, and "create" for a few new files), whereas the Linux
> machines transfer all the files (the log contains similar "create d"
> and "create" entries, as well as "same" entries for ALL the unchanged
> files).
>=20
> This is most apparent on the dual-boot machine as some incrementals
> are small and fast, whereas others are large and slow. Here is the
> backup listing for that machine. Note that backups 1, 3, 7, and 10
> were all when it was booted Linux, the others were all Windows.
>=20
>                          Totals         Existing Files     New Files
> Backup# Type	#Files 	Size/MB	MB/sec 	#Files 	Size/MB #Files 	Size/MB
> 0 	full 	4905 	2239.8 	3.21 	225 	8.2 	5072 	2231.7
> 1 	incr 	4905 	2239.8 	10.37 	4906 	2239.8 	391 	0.1
> 2 	incr 	7 	5.7 	0.08 	18 	1.8 	42 	3.9
> 3 	incr 	4905 	2239.5 	3.94 	4904 	2239.2 	3 	0.4
> 4 	incr 	8 	5.8 	0.08 	2 	2.0 	10 	3.8
> 5 	incr 	8 	5.9 	0.08 	2 	2.0 	8 	3.8
> 6 	incr 	8 	5.9 	0.09 	2 	2.0 	10 	3.9
> 7 	incr 	4905 	2239.7 	12.65 	4900 	2235.9 	9 	3.8
> 8 	incr 	8 	5.9 	0.09 	7 	5.6 	2 	0.4
> 9 	incr 	34 	24.6 	0.35 	26 	20.2 	14 	4.4
> 10 	incr 	4730 	2140.5 	18.61 	4725 	2136.6 	11 	3.9
> 11 	incr 	34 	24.7 	0.37 	28 	20.6 	11 	4.0
>=20
> I suspect this is somehow related to checksum caching, but I have
> enabled the checksum-seed option globally and I think all the rsync's
> I'm using should have it available. Is there something else in the
> cygwin-rsyncd-2.6.2_0.zip version of rsync that is speeding up the
> Windows backups? Can I somehow get that on my Linux machines too?

Yes, the entire set of files is being transferred on an
incremental with a linux boot.

That means some meta data (eg: uid, gid, mtime, size) is being
delivered differently to rsync on windows vs linux.

It is quite possible that the uid and gid are different when you boot
windows vs linux.  It might be related to file time stamps.  What type
of file system is this?  If it is FAT then you are likely a victim of
the DST problem.  Google "rsync FAT DST".

I recommend doing some manual rsyncs and seeing what meta data
you get after the transer with windows vs linux.

Craig