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Bug#511602: Suggestions for lowmem installs (e.g. mount ext3 as ext2)

Package: lowmem
Severity: minor

John Reiser made some very interesting comments about the installer on
a machine with little RAM.  I particularly like the suggestion of
mounting the ext3 partition as ext2 - maybe this should be done in
lowmem mode.

----- Forwarded message from John Reiser <vendor@BitWagon.com> -----

From: John Reiser <vendor@BitWagon.com>
Subject: Re: Please test debian-installer rc1 images
Date: Sun, 09 Nov 2008 09:15:52 -0800
To: debian-arm@lists.debian.org
User-Agent: Thunderbird (X11/20080723)

> debian-installer rc1 is going to be announced officially next week.
> However, the images for ARM are already available.  ...
> http://www.cyrius.com/debian/nslu2/files/tmp/daily.img

It worked for me but it was very slow, by a factor of ten.
It took 3 hours and 15 minutes to install 278MB of Base system only.
That's an aggregate rate of 24 KB/s for a USB2.0 flash memory device
that can write at 8.5 MB/s.  [WLAN was 1.5 Mb/s DSL; the download
total of about 150 MB takes about 17 minutes.]

Changing from ext3 to ext2 (which avoids the "double write" of
journalling), and using the 'noatime' mount option, saved 45 minutes.
  [You can convert quickly from ext2 to ext3 at your leisure:
   although the partitioner's choice of option flags is different:
     ext3: ext_attr resize_inode dir_index filetype sparse_super large_file
     ext2:                                 filetype sparse_super
   If ext3 is the ultimate goal, then perhaps the partitioner
   should mkfs an ext3 filesystem, but it should be mounted as ext2
   during the install.
The Base system finished in two hours, then the installer spent
half an hour doing "nothing" because I unchecked the pre-selected
"Standard system" option of "Select and install software."  Many
minutes of that half an hour was spent running 'aptitude' with a
VSZ of 48MB on machine with only 32MB of RAM.  Perhaps this half hour
can be avoided by running the installer in Expert mode, and entirely
omitting the step "Select and install software."

There are blocking interactive dialogs at the begining of "Select and
install software" which occur after a couple hours.  It is poor design
of the overall process to require "tending" such an operation.  Instead,
the default should be to limit interaction to the beginning of the
whole process.

The debian-installer "Low memory mode" should be viewed as a last resort.
Instead, build the complete filesystem image on resource-rich machine
(large RAM, fast CPU, fast disk) then download the result.  Or create
the empty filesystems, export them using NFS, and do a "remote" install
from another machine on the local network.


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----- End forwarded message -----

Martin Michlmayr

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