Well, yes, it can if the number of tagged commands you throw at a device overloads the sequencer so it can never really get started on the first command. If you don't disconnect, you don't throw multiple commands at the disk. I don't remember from the original mail whether or not this was a raw device or not.
On Sat, 20 Feb 1999, Matthew Dillon wrote: > :This did not improve anything , but I think I have found the couse. > :In that modepage there is a DISC value which was 0 on the IBM and 1 on the > :Seagate. I remembered a ' Enable disconnect' option in the Adaptec 2940 > bios, > :setting this to 'off' for both harddisks led to a huge performance increase > on > :the Seagate. If I also enable Ultra mode iozone write goes from 1.5 MB/s > :to 12 MB/s ( a factor of 8 !!!). > : > : Paul > : > :-- > :Paul van der Zwan paulz @ trantor.xs4all.nl > > There's something wrong. Disconnection should not cause that sort > of performance decrease. Disconnection is necessary if you want to > maintain preformance with more then one scsi device on the scsi bus. > > -Matt > Matthew Dillon > <dil...@backplane.com> > > > > To Unsubscribe: send mail to majord...@freebsd.org > with "unsubscribe freebsd-current" in the body of the message > To Unsubscribe: send mail to majord...@freebsd.org with "unsubscribe freebsd-current" in the body of the message
