Hello,
2015-01-23 20:04 GMT+01:00 Dimitri Maziuk <dmaz...@bmrb.wisc.edu>:
> On 01/23/2015 12:22 PM, Radosław Korzeniewski wrote:
>
> > If you are using a vchanger then I guess it is a disk only backup, so why
> > do you spool data? It is not required but making you backup slow down at
> > least 2 times then standard job.
>
> It's 2 times slower if your spool/despool is strictly sequential and the
> same size pipes go in and out. If you have 10 clients spooling over a
> 1Gb/s link, that's roughly 10MB/s/client. Iostat clocks ext4/basic sata
> drives at around 110MB/s write speed, so despooling is 10 times faster.
>
I think you should read what a data spooling really is in Bacula. Sorry.
It is useful only for tape drives to avoid shoe-sine of tapes.
When used with disks it will slow down every backup job, no matter how many
of them you will run.
If only the clients could keep the pipe full, it could be ~10 times
> faster than the "standard" job.
No, it is not working as you described.
Data spooling will read stream from the client, then write it to the
temporary disk file, then during despool it is stopping a stream from the
client, reads a temporary file and write to destination volume.
A standard job will never stop reading a stream and direct write data to
the volume.
In a purely hypothetical perfectly
> spherical world of uniform density, obviously, but still: no, 2x slow
> down is not how it really works.
>
Yes it is. Every job will be slower. I had this kind of setup for tuning
and I realized that I can speed up every backup Job when I disable data
spooling.
You should distinguish between attributes spooling, data spooling and
spooling for tapes vs disks.
best regards
--
Radosław Korzeniewski
rados...@korzeniewski.net
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