Howdy, > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of Peter Wemm > Sent: Tuesday, 9 July 2002 12:44 > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: Re: offtopic: low level format of IDE drive. > > [snip] > > Does anyone have a detailed list of which SCSI drives do > > track writes rather than sector writes? > > You can find out by turning write caching on and off. > camcontrol modepage daN. You want -m 8, the WCE bit. (write cache > enable). I do not remember which -P args you need. > > If you see a HUGE difference in writing smallish blocks to disk > between WCE on vs off, then you have a track write drive. > > A true sectored drive would have much less of a slowdown. I do > not have a comparable set handy to get a better idea of what to > expect. > Really small writes cost scsi overhead though, so that adds to > the slowdown. If I was to take a best guiess, I would expect a > factor 10+ slowdown for track-write drives on 4K blocksize writes, > vs factor 2-5 slowdown for a sectored drive. > This is the slowdown factor when turning WCE off. > Excellent. This information should prove invaluable for future drive testing and acceptance. Thanks.
> Cheers, > -Peter Regards, Chris Knight Systems Administrator AIMS Independent Computer Professionals Tel: +61 3 6334 6664 Fax: +61 3 6331 7032 Mob: +61 419 528 795 Web: http://www.aims.com.au To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
