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Re: Why does NTFS compression reduces size of .pack-files by ~50 %?

From: Nathan Hartman <hartman.nathan_at_gmail.com>
Date: Thu, 26 Sep 2019 10:22:43 -0400

On Sat, Sep 21, 2019 at 10:15 AM Thorsten Schöning <tschoening_at_am-soft.de>

> Hi all,
> I have some repo generating revisions automatically based on some
> events of some software, to track some changes to some status and
> config files automatically. This repos currently contains ~ 145'000
> revisions and because the overhead of individual files is pretty high,
> I'm packing them once a week.
> That repo currently has a size of ~750 MiB on disk and I have a backup
> on my Windows using NTFS. Just out of interest I enabled file system
> compression for that repo and found that the storage needs could be
> reduced to ~350 MiB of data.
> That was pretty surprising for me, because some months ago I enabled
> zlib compression level 9 and fully dumped/loaded that repo to benefit
> of the compression. NTFS compression is known to prefer performance in
> favour of overall savinbgs, so I would have expected to not get much
> difference.
> Looking at some of the pack files, there's a lot of ASCII and blocks
> of binary 0s in them. Maybe NTFS compression is benefitting of those?
> In general, is the data in the pack files for revs compressed or not?
> From my understanding the data of the individual revs is reused and if
> that is compressed, the pack files are as well. Looking at fsfs.conf,
> compression for packed revprops need to be enabled additionally, but
> that really only applies to the revprops, correct? Those don't count
> much in my scenario.
> Is there any way to further optimize/compress the pack files using SVN?
> My repos are hosted under Linux using ext4, if it's normal what I see
> and can't be optimized further using SVN itself, I 'm considering
> switching to BTRFs with it's file system compression. Going to see the
> same benefits like for NTFS pretty likely.
> Thanks for your advices!
> Mit freundlichen Grüßen,
> Thorsten Schöning

Interesting. I'll try running some tests on my systems. It will probably
take me a week or so to get to it since I have a big backlog of things at
the moment.

A few questions:

Which SVN server version?

Which compression type?

Have you tried a dump and load lately to see if the resulting repository is
Received on 2019-09-26 16:23:08 CEST

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