restore(8) to USB key: terrible slow

[Matthias Apitz]

El día Wednesday, November 17, 2010 a las 01:52:59PM +0000, Alexander Best escribió:

> > > Thanks; I have to build a kernel for this ...
> > > 
> > > When I write the key just with dd(1) it performs normal with big blocks:
> > > 
> > > # dd if=/home/guru/usb9root.dmp of=/dev/da0 bs=1m count=100
> > > 100+0 records in
> > > 100+0 records out
> > > 104857600 bytes transferred in 16.650550 secs (6297546 bytes/sec)
> > > 
> > > and slow with 512 byte blocks:
> > > 
> > > # dd if=/home/guru/usb9root.dmp of=/dev/da0 count=100
> > > 100+0 records in
> > > 100+0 records out
> > > 51200 bytes transferred in 1.997130 secs (25637 bytes/sec)
> > > 
> > > any idea or do we need the debug output?
> > > 
> > > 	matthias
> > 
> > What block size does the dump utility use?
> 
> dump(8) says 10k.

The -b of dump(8) is for the output device (which in my case was a plain
file, and the 3 GByte was dumped in ~10 minutes). I think it does not
influence the write performance of restore(8).

Interestingly, after the above write with dd(1) over sector 0 (...) and
after recreating the FreeBSD layout on the key (fdisk(8),
bsdlabel(8), newfs(8)), the restore(8) now works much faster.

There are a lot of small files (a complete /usr/src/sys after SVN checkout
with all SVN control files) and a complete FreeBSD live system in this
dump(8).

The dump(8) and restore(8) is only to make from a 16 GByte bootable USB key
with a lot of free space on it a smaller 4 GByte key to give it away to
some FreeBSD lovers in Cuba so that they can distribute it there, not
needing such a big 16 GByte USB key. Any other idea to shrink a 16 GB
file system to 4 GB on a 2nd key?

	matthias
-- 
Matthias Apitz
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