Re: [Moosefs-users] Backing up MFS metadata

[Roast <zha...@gm...>]

Thanks,Michał Borychowski.

2010/7/19 Michał Borychowski <mic...@ge...>

>  Please read this article:
> http://www.moosefs.org/news-reader/items/metadata-ins-and-outs.html
>
>
>
> The most important part for you is here:
>
> *The metalogger will download the metadata.mfs.back file on a regular
> basis (by default every 24 hours) from the master server. The downloaded
> file is saved with the file name metadata_ml.mfs.back. Similarly, it also
> continuously receives the current changes from the master server and writes
> them into its own text change log named changelog_ml.0.mfs. Where these
> files are also rotated every hour up to the configured maximum number of
> change log files (see man mfsmetalogger.cfg).*
>
>
>
> Yes, you can fully restore metadata from files saved by metalogger.
>
>
>
> If you need any further assistance please let us know.
>
>
>
>
>
> Kind regards
>
> Michał Borychowski
>
> MooseFS Support Manager
>
> _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
>
> Gemius S.A.
>
> ul. Wołoska 7, 02-672 Warszawa
>
> Budynek MARS, klatka D
>
> Tel.: +4822 874-41-00
>
> Fax : +4822 874-41-01
>
>
>
> *From:* Roast [mailto:zha...@gm...]
> *Sent:* Friday, July 16, 2010 1:45 PM
> *To:* Michał Borychowski
> *Cc:* Stas Oskin; moosefs-users
>
> *Subject:* Re: [Moosefs-users] Backing up MFS metadata
>
>
>
> Another question.
>
> Does master server sync the change log to metalogger server in real time?
>
> And if so, we can restore the full meta info from the metalogger server. Am
> I right?
>
> 2010/7/15 Michał Borychowski <mic...@ge...>
>
> You can backup changelog files (you would need just the two newest ones -
> "0" and "1"). You can make these backups even every minute. So you can have
> potentially lost information for about 1-2 minutes.
>
>
>
> But the question is - why to back up changelogs manually? Metalogger
> machines are dedicated to this. You can have as many metalogger machines on
> the network as you like. And metalogger process can be run on any computer,
> even an older one.
>
>
>
>
>
> Regards
>
> Michał
>
>
>
>
>
>
>
> *From:* Stas Oskin [mailto:sta...@gm...]
> *Sent:* Friday, July 09, 2010 2:27 PM
> *To:* Fabien Germain
> *Cc:* moo...@li...; Michał Borychowski
> *Subject:* Re: [Moosefs-users] Backing up MFS metadata
>
>
>
> Hi.
>
>
> As for the time it takes, it depends on the number of chunks you have, and
> the hardware server you use (CPU + HDD speed). For example in our case (15
> million chunks, 6 GB of metadata), it takes between 1 and 2 minutes on a
> Xeon processor.
>
>
> I actually meant, how much time backwards could be recovered by replaying
> all the logs?
>
> Michael said that backup log is created every hour so up to 1.5 hour can be
> potentially lost.
> If all the logs are replayed, can the data be consistent up to the moment
> of crash?
>
> Regards.
>
>
>
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