ufs2 / softupdates / ZFS / disk write cache

[Dan Naumov]

2009/6/21 Šimun Mikecin <numisemis at yahoo.com>

>
> 21. lip. 2009., u 13:41, Andrew Snow <andrew at modulus.org> napisao:
> > Folks who need to maximize safety and can't afford the performance
> > hit of no write cache need to do what they always have had to do in
> > the past - buy a controller card with battery-backed cached.
>
> Or:
> B) use SCSI instead of ATA disks
> C) use UFS+gjournal instead of UFS+SU
> D) use ZFS instead of UFS+SU


Actually I think a need a few clarifications regarding ZFS:

1) Does FreeBSD honor the "flush the cache to disk now" commands issued by
ZFS to the harrdive only when ZFS is used directly on top of a disk device
directly or does this also work when ZFS is used on top of a
slice/partition?
2) If we compare ZFS vs UFS+SU while using a regular "lying" SATA disk (with
write cache enabled) under heavy IO followed by a power loss. Which one is
going to recover better and why?


Sincerely,
- Dan Naumov