rsync performance

[Tim Moore]

Try using major subdirectories one level lower.  Example sequence from my 
automated home machine backup:

rsync -ax --stats / /rsync_backup/
rsync -ax --stats /usr/ /rsync_backup/usr/
rsync -ax --stats /home/ /rsync_backup/home/

Compare to "rsync -a --stats / /backup/"

Ralf Fassel wrote:
> We're using rsync 2.6.3 to sync two DELL PowerEdge servers with both
> Redhat-EL4 and otherwise nearly identical hardware (2.8/3GHz, 1GB RAM
> each).  The source machine has a SCSI-RAID1, the destination a
> SATA-RAID1 disk attached.
> 
> There are 5 filesystems which are rsynced via ssh.  On the smaller
> filesystems with ~200.000 files/7GB, rsync takes 1-3 minutes:
>     lion:/atg/ ========= Tue Aug 22 12:13:29 CEST 2006 ==================
>     receiving file list ... done
>   --<snip-snip>--
>     Number of files: 233780
>     Number of files transferred: 2
>     Total file size: 6716087965 bytes
>     Total transferred file size: 1470 bytes
>     Literal data: 1470 bytes
>     Matched data: 0 bytes
>     File list size: 5015765
>     Total bytes sent: 68
>     Total bytes received: 5017339
> 
>     sent 68 bytes  received 5017339 bytes  56060.41 bytes/sec
>     total size is 6716087965  speedup is 1338.56
>     lion:/homes/ ========= Tue Aug 22 12:14:58 CEST 2006 ==================
> 
> 233780 files/89 sec = 2626 files/sec
> 
> On the large filesystems with ~1.200.000 files/17GB, rsync takes 30
> minutes, even when only few files change (and even when invoked with -n):
>     lion:/homes/ ========= Tue Aug 22 12:14:58 CEST 2006 ==================
>     receiving file list ... done
>   --<snip-snip>--
>     Number of files: 1232323
>     Number of files transferred: 124
>     Total file size: 17103825898 bytes
>     Total transferred file size: 1416942923 bytes
>     Literal data: 27658581 bytes
>     Matched data: 1389311598 bytes
>     File list size: 95325482
>     Total bytes sent: 643209
>     Total bytes received: 123363867
> 
>     sent 643209 bytes  received 123363867 bytes  62963.73 bytes/sec
>     total size is 17103825898  speedup is 137.93
>     lion:/homes/atg/ ========= Tue Aug 22 12:47:48 CEST 2006 ==================
> 
> 1232323 files / 1960 sec = 629 files/sec
> 
> In comparison, on the large filesystem, 'find'ing all files on the
> source system and 'stat'ing them takes 1.75 minutes:
>     source# time find /homes -xdev -print0 | xargs -0 stat -c "%s %Y" | wc -l
>     1232287
>     real 1m41.987s
>     user 0m7.075s
>     sys	 0m33.216s
> On the destination 4 minutes:
>     dest# time find /backup/lion-homes -xdev -print0 | xargs -0 stat -c "%s %Y" | wc -l
>     1233202
>     real 4m3.650s
>     user 0m9.895s
>     sys	 0m41.047s
> 
> Receiving the 123363867 bytes should not take longer than 20sec on a
> 100Mbit LAN, and transferring a GB to disk should not take longer than
> say a minute (we have write transfer rates of ~50MB/sec on those disks
> on each machine).
> 
> So what is rsync doing in addition that it takes >30 minutes to sync
> the large filesystem?
> 
> Thanks
> R'

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