Date: Fri, 22 Sep 1995 21:25:15 +1000 From: Bruce Evans <bde@zeta.org.au> To: cvance@cfar.umd.edu, hardware@freebsd.org Subject: Re: Adaptech 1542 & 3Com 3c509 conflict? Message-ID: <199509221125.VAA03283@godzilla.zeta.org.au>
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>I seem to have some sort of conflict between my network interface and >scsi disks. The scsi controller is an adaptech 1542CF and the eth >adapter is a 3c509. >Basically, the network is slow writing to a scsi disk, and fast the >rest of the time. Has anyone seen this before? Can anyone suggest >something I could do to fix the situation? Perhaps the scsi disk is inherently slower for the type of work given to it by ftp. This is not unlikely, since ftp's writes are poorly buffered and scsi disks often have a very high command overhead. ktracing ftp here showed the following sequence of write sizes: ..., 0x5a0, 0x10e0, 0x2760, 0xb40, 0x5a0, 0x10e0, 0x2760, 0x1c20, ... The speed over ethernet (WD8013EBT) for ftp'ing a 15MB file to a slow scsi disk and to /dev/null were the same (about 440K/sec, probably limited by the slow IDE disk on the server). This was faster than for ftp'ing from localhost and the same speed as cp'ing from the same file system in some cases (cases where the buffer cache cannot help and where clustering is apparently ineffective). Bruce
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