Re: [PATCH] 2.4.x write barriers (updated for ext3)

James Bottomley
2002-03-01T16:00:44Z

Dieter.Nuetzel@hamburg.de said:
> How do you checked it?

I used sginfo from Doug Gilbert's sg utilities (http://www.torque.net/sg)

The version was sg3_utils-0.98

Dieter.Nuetzel@hamburg.de said:
> But when I use "scsi-config" I get under "Cache Control Page": Read
> cache enabled: Yes Write cache enabled: No

I believe write cache enabled is the state of the WCE bit and read cache
enabled is the inverse of the RCD bit, so you have a write through cache.

I think that notwithstanding the spec, most drives are write through (purely
because of the safety aspect). I suspect certain manufacturers use write back
caching to try to improve performance figures (at the expense of safety).

James