ufs2 / softupdates / ZFS / disk write cache

[Simun Mikecin]

Andrew Snow wrote:

> All of these solutions still involve disabling of write cache, with a performance hit of varying degrees. (I have tried all of those except gjournal!)
Can you please elaborate this statement? AFAIK all of these solutions are absolutelly safe to use with write cache enabled:
- SCSI disks are safe with TCQ enabled (not sure when TCQ is disabled)
- UFS+gjournal is safe because of regular disk cache flushing
- ZFS is safe by design