Re: rsync and streaming replication

2011/11/17 Jean-Armel Luce <jaluce06@gmail.com>:
>
> 2011/11/16 Scott Ribe <scott_ribe@elevated-dev.com>:
>>
>> > Does the network connection have high latency?
>
>  When I ping the server,time=15ms.
>
>> > Also, I believe you said -z seemed to slow it down?
>
> I confirm
>
>> >
>> > I'm certainly glad that you've got a 3x speed increase--
>
> Me too :-) . Thanks for your advices. Thanks to Cédric too

you're welcome.

> ;
>>
>> But still, something seems odd about the performance you've reported, so
>> I'm left wondering about what could cause that. Disk performance glitch at
>> one end or the other, network performance, CPU load???
>
> CPU usage is very low

strange (added to the -z making things worse). there should be
something behind as supposed Scott.
Virtual host ? Firewall ? something not common ?

>
> Today, I tried with command : rsync -rc --block-size=8192
> Rsync duration with blksize=8192 was 31 minutes (yesterday without
> blocksize, duration was 32 minutes exactly)

idea behind the blocksize changes was also to reduce the number of
checksum comparaison and alignement (by 8) and compare with the rsync
with --ignore-time instead of --checksum
That should give a good idea on the extra cost of the block checksum
for files without changes (which are matched by --checksum).

--
Cédric Villemain +33 (0)6 20 30 22 52
http://2ndQuadrant.fr/
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