[tahoe-dev] timestamps on mutable files

Kevan Carstensen kevan at isnotajoke.com
Mon Jan 4 18:24:17 UTC 2010


I'm sure someone will correct me if I'm wrong, but I think #694  
removed the hard limit on mutable files. So your data should be backed  
up.

(apologies for formatting - I'm on a phone)
--
Kevan Carstensen | <kevan at isnotajoke.com>

On Jan 4, 2010, at 10:10 AM, Jody Harris <imhavoc at gmail.com> wrote:

> Ack!
>
> So, I'm NOT backing up my data!? (I'm just backing up the first 2MB  
> of each compressed table?)
>
> Okay, if immutable files are my only choice, how do I do garbage  
> collection to insure that a minimum of dead space is taken up by  
> "yesterday's" files?
>
> jody
> ----
> - Think carefully.
> - Contra mundum - "Against the world" (St. Athanasius)
> - Credo ut intelliga - "I believe that I may know" (St. Augustin of  
> Hippo)
>
>
> On Mon, Jan 4, 2010 at 11:05 AM, Peter Secor <secorp at allmydata.com>  
> wrote:
> Mutable files currently have a small (2MB?) limit and cannot be used  
> for
> larger files. Immutable files (the default) have a much higher limit
> (12GB now?) and are much better suited for the purpose you described  
> of
> large snapshots of data that won't change later.
>
> There are ideas behind larger mutable files (#393) but they are not
> implemented yet.
>
> Ps
>
> On 1/4/10 7:37 AM, Jody Harris wrote:
> > Oh, I forgot to answer the "how?"
> >
> > ... put --mutable ...
> >
> > jody
> > ----
> > - Think carefully.
> > - Contra mundum - "Against the world" (St. Athanasius)
> > - Credo ut intelliga - "I believe that I may know" (St. Augustin  
> of Hippo)
> >
> >
> > On Sun, Jan 3, 2010 at 10:59 PM, Jody Harris <imhavoc at gmail.com
> > <mailto:imhavoc at gmail.com>> wrote:
> >
> >     I have a script that:
> >       - iterates though my MySQL tables
> >       - dumps each table
> >       - pipes the dump through gzip
> >       - write the file to a temp file
> >       - copies the file to [remote storage] (now Tahoe grid)
> >       - deletes temp file
> >
> >     This gives me a daily snapshot of all of the active databases  
> on my
> >     server every night.
> >
> >     The current backup is ~ 300 MB/night, which isn't bad, but  
> after one
> >     year, that's 110+GB x 3.3 and counting of consumed tahoe space.
> >     Unless tahoe has a better garbage collection system than I  
> have come
> >     to believe, that's going to be a problem on a 500 GB grid.
> >
> >     In my reading of the tahoe docs, I have not come across any  
> alarms
> >     concerning mutable files. Is there something I should be made  
> aware of?
> >
> >     jody
> >     ----
> >     - Think carefully.
> >     - Contra mundum - "Against the world" (St. Athanasius)
> >     - Credo ut intelliga - "I believe that I may know" (St.  
> Augustin of
> >     Hippo)
> >
> >
> >     On Sun, Jan 3, 2010 at 10:50 PM, Zooko O'Whielacronx
> >     <zookog at gmail.com <mailto:zookog at gmail.com>> wrote:
> >
> >         On Sun, Jan 3, 2010 at 10:33 PM, Jody Harris
> >         <havoc at harrisdev.com <mailto:havoc at harrisdev.com>> wrote:
> >          > I have set up my web server to store backup files on my  
> tahoe
> >         grid, shifting
> >          > from the use of a server at my house. One thing that
> >         initially alarmed me
> >          > was that the timestamps of the backed up files is not  
> updated
> >         in the
> >          > tahoe-lafs interface. I did confirm that the shares
> >         timestamps are updated.
> >
> >         Tahoe-LAFS doesn't store timestamps or other metadata on  
> files, only
> >         on links to files, which links are stored in directories.   
> So if you
> >         have a directory which contains a link named "README.txt" to
> >         version 1
> >         of your file, and then you upload version 2 of your file  
> and you
> >         change that directory to link to version 2, then Tahoe- 
> LAFS will
> >         update the timestamp on that link named "README.txt" when  
> it updates
> >         the link to point to the new file.
> >
> >         Did you say "mutable files"?  You should probably not be  
> using
> >         mutable
> >         files for anything.  Immutable files (plus directories)  
> probably fit
> >         all your needs for backups, and mutable files have  
> significant
> >         performance problems.
> >
> >         How do you trigger these backups -- are you using "tahoe  
> cp" or
> >         "tahoe
> >         backup" or sending HTTP requests to the WAPI or something  
> else?
> >
> >         Regards,
> >
> >         Zooko
> >         _______________________________________________
> >         tahoe-dev mailing list
> >         tahoe-dev at allmydata.org <mailto:tahoe-dev at allmydata.org>
> >         http://allmydata.org/cgi-bin/mailman/listinfo/tahoe-dev
> >
> >
> >
> >
> >
> > _______________________________________________
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> > tahoe-dev at allmydata.org
> > http://allmydata.org/cgi-bin/mailman/listinfo/tahoe-dev
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