Sysinstall automatic filesystem size generation.

[Matthias Buelow]

Mark Kirkwood wrote:

>>>FreeBSD's filesystems are very robust should you lose power.
>>This sentence is completely bogus (or at best: wishful thinking)
>>and should be deleted.
>It's probably correct if you have hw.ata.wc=0 (and are using IDE drives 
>obviously).

I'd like to stress the "probably". I've already seen unrepairable
filesystem corruption with softupdates enabled in the past with
"good" scsi disks at power loss. Furthermore, disabling the write-back
cache in a typical consumer (read: typical PC workstation) environment
today, with large IDE/SATA drives, is unrealistic because of the
severe performance degradation, and might even be counter-indicated
due to the increased wear&tear on the disk, which might significantly
reduce the disk's lifetime. Softupdates works only in an idealized
environment that doesn't match against reality.  In addition, with
softupdates there seems to be a much higher probability of losing
files, as I have observed.. that is, getting them zero-truncated,
or even deleted (which shouldn't happen in that scenario, I'm sure
I've seen the results of a bug), than without. Do I still use
softupdates?  Yes, because of the performance benefit, but I don't
treat it as much different than completely asynchronous operation,
with the only difference that it's a slightly more resilient in
case of a kernel crash (vs.  a power outage) and I make frequent
backups.

mkb.