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Re: svntar, anybody?

From: Erik Huelsmann <ehuels_at_gmail.com>
Date: 2007-07-04 13:23:11 CEST

Could this discussion be moved to users@ please, as it's obviously not
about developing Subversion itself anymore?

Thanks in advance!

bye,

Erik.

On 7/4/07, Ph. Marek <philipp.marek@bmlv.gv.at> wrote:
> On Mittwoch, 4. Juli 2007, Talden wrote:
> > > > A
> > > > tar based approach will seek the length of the tar to evaluate
> > > > differences to sync.
> > >
> > > It won't seek, it will just push that to the clients to apply.
> > > And linear reading is on the >100MByte/sec range, eg. for a cheap stripe
> > > set of two harddisks.
> >
> > Assuming of course that only one client pulls at a time. If not then
> > you depending upon disk cache to avoid seeking. A large RAM
> > investment might be coming your way.
> The difference is still between having a few (self-synchronizing) points that
> are read in a single file vs. having many files being read randomized.
>
> See here:
>
> Tar-file ===================================================================
> ^ ^
> Client1 |
> Client2
>
>
> These two clients will synchronize, until they both send identical data -
> because Client2 will have to fetch from disk, while Client1 can use already
> cached data and is thus faster.
>
>
> Tar-file ===================================================================
> ^ ^ ^ ^
> Client1 | Client3&4 Client5-8
> Client2
>
> After a while there'll be (at most) a few points in the file being read; using
> the anticipatory io-scheduler and/or read-ahead it's easy to only seek, say,
> 3 or 4 times a second while keeping the bandwidth at maximum speed.
>
>
> Compare that with 8 clients reading physically discontinuos regions from the
> harddisk, with additional CPU load ....
> Sure, that data *should* be cached after the first reading ... but there's a
> lot more to cache: indizes from the repository, inodes for the revision
> files, and just the seeking around for "Client3&4" above takes most of the
> harddisk bandwidth.
>
>
> Regards,
>
> Phil
>
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Received on Wed Jul 4 13:23:10 2007

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