More experiences with Spherical Cow

[John Reiser]

> so I'll measure Fedora 17 Release (x86_64) on 3GHz CPU, 8GB RAM, SATA II:
> 
>    Duration   Activity
>    ========   ========
>      12m26s   write DVD+RW  (3.8GB; 4X)
>       5m00s   write DVD+R   (3.8GB; 16X)
>      -=-=-=-
> 
>       3m48s   Boot DVD+R, go until "Starting installation process"
>       2m32s   Starting installation process
>       9m32s   install 1207 packages (default Gnome Desktop; 4.1GB)
>       2m56s   create yum package database using links in filesystem
>      ------
>      18m48s   installation
>       5m00s   media preparation
>      ======
>      23m48s   .iso-to-installed

Doing the same thing on the same hardware, except with the installation source
on a USB2.0 flash memory device with vfat filesystem:

       38m58s   livecd-iso-to-disk
       -=-=-=-

        3m22s   Boot DVD+R, go until "Starting installation process"
        0m12s   Starting installation process
        8m10s   install 1207 packages (default Gnome Desktop; 4.1GB)
        3m09s   create yum package database using links in filesystem
       ------
       14m53s   installation
       38m58s   media preparation
       ======
       53m51s   .iso-to-installed

Note the factor of 12.7 speedup for "Starting install process": 12s instead of 2m32s.
This shows how much faster seeking is on the flash device instead of on the DVD+R.
The installation is almost 4 minutes faster (21%) using the flash device,
but media preparation takes about 34 minutes longer (a factor of 7.6)

livecd-iso-to-disk spends nearly all its time transferring the Packages
directory using rsync.  I wonder how much might be saved if vfat supported
the fallocate() system call (and rsync used it.)

The flash memory device might be considered slow:
   dd if=/dev/flash bs=32k count=10000 of=/dev/null
transfers 328MB in 19.3 seconds, which is an average of 17.0 MB/s.

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