RELEASE discs & ISO images (for future)
olli at lurza.secnetix.de
Tue Mar 18 06:59:59 PDT 2008
Vadim Goncharov wrote:
> Oliver Fromme wrote:
> > [...]
> > > > 224655360 7.0-RELEASE-i386-livefs.iso
> > > > 94493696 7.0-RELEASE-i386-livefs.iso.uzip (16k cluster)
> > > > 110188032 7.0-RELEASE-i386-livefs.iso.uzip (2K cluster)
> > > >
> > > > So the difference is 124 MB for 16K cluster size, and
> > > > 109 MB for 2K cluster size (which is noticably faster
> > > > during access). Actually the space savings will be a
> > > > bit less, because the /boot directory (about 30 MB)
> > > > won't be compressed. So the real gain is probably a
> > > > little less than 100 MB in the 2K case.
> > >
> > > By the way, the maxmum cluster size is 127k or 130048 with uzip,
> > > if you want to maximize the compression ratio.
> > That would make the live FS painfully slow, and it wouldn't
> > make a big difference from the default (16K).
> > It is already noticeably slow with the default cluster size
> > of 16K on my test machine (a 1 GHz VIA C3), so would rather
> > prefer to use 2K cluster size, even though compression will
> > be not quite as good. (2K is the minimum, less than that
> > doesn't make sense for CD9660 media because the physical
> > sector size is 2K.)
> How much is slowdown from 2K to 16K ?
It's very noticeable. I haven't done benchmarks, but
you can clearly feel the difference. A find(1) takes
more time. Also man(1) takes longer until the page
comes up. Any kind of random access is slower, unless
all data is already cached.
Interestingly there doesn't seem to be a difference
between 2K and 4K, and the difference to 8K is only
very small. But there is a noticeable difference
between 8K and 16K. I don't know why, maybe it's
related to FreeBSD's handling of FS buffers. So
maybe the "optimal" cluster size for an acceptable
performance/compression ratio would be 8K.
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
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