Re: [Bacula-users] how to debug a job

Hello,

2015-01-23 20:04 GMT+01:00 Dimitri Maziuk <dmaziuk AT bmrb.wisc DOT 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
radoslaw AT korzeniewski DOT net

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