Re: gbde data corruption?

Hi Poul,

> >apparently updating g_bde_crypt.c from rev 1.12 to 1.13 has effects on the
> >format of data or the layout of the encrypted filesystem. the stuff that
> >was on that mount with the old kernel is gone now.
>
> Yes, I fumbled a commit and slipped in some debugging code in 1.12.

judging by your commit message, at first i thought that 'debugging'
implied only some lack in performance - or too much verbosity.

> I've had 1.13 running my toture-test here for 38 hours now with no
> trouble.

i'll stress-test it some more after i get to reboot that machine
physically this evening. mounting the filesystems that used to make some
sense with 1.12 after upgrading to 1.13 apparently hanged the machine
after some short time.

my hope is to eventually have an nfs server (200gb data is waiting to live
on it) that can saturize 100mbit - and is also reliable :)

how much (incompatible) change in the format of the gbde data do you
expect ? can i hope for something stable in 5.1, for example ?!

> >> PS: i also have some performance issues with gbde, about which i'll whine
> >> some other time :) it seems to me that the transactions on the disc (the
> >> way i use gbde at least) are too small to reach the theoretical speed of
> >> the harddrive.
>
> Much worse than that:  They get cut into smaller I/O requests and the
> cpu has to chew on them a lot.  While GBDE is not directly slow, it
> will never be as fast as an unencrypted partitition.

hm... cpu seems to be not the limiting factor at all - that machine has an
athlon 1800+ and is idle >>50% most of the time. without understanding the
technical details, it seems to me that working on bigger chunks of the
disc at a time would result in much more throughput.

in general, as long as the cpu is not maxed out, shouldn't only latency -
but not throughput - be impacted by using gbde?

in absolute terms: getting approximately 1,5MB/s for writing access on a
relatively modern harddisk seems quite low to me. does the data get
scattered on the physical disc, or what could cause this ?

read access is less tragic - approx 10MB/s (compared to slightly over
20MB/s on the same drive with a non-gbde mount) - but i also don't quite
understand what leads to that.

regards, thanks for the quick reply,

Heiko