magic sysrq keys functionality

[Matthias Andree]

Scott Long <scottl at freebsd.org> writes:

> GAH!  No, please don't start this war again!  The last time that we tried
> turning this off in a release (4.1 IIRC), were were plagqued by months of
> earthquakes, plagues, and deaths of first-born youngsters.  I 100% agree
> that write caching in ATA is not compatible with data integrety, but the
> ATA marketting machine has convinced us that cached+untagged speed is
> better than uncached+tagged safety.  C'est la vie, or so they say here.

Looking out of the cosy FreeBSD hut, for the Linux kernel, write barrier
support (i. e. using the ATA cache flush facility on those drives that
support it, and logging a warning if a drive doesn't) to enforce proper
write order and synchronization is underway, with some distros already
using it, for instance SuSE. It's not yet in the baseline code AFAIK.

BTW, is proper write order guaranteed on SCSI drives through ordered
tags? softdep doesn't really like blocks being written in different
order than scheduled.

-- 
Matthias Andree

Encrypted mail welcome: my GnuPG key ID is 0x052E7D95 (PGP/MIME preferred)