Date: Sat, 7 Oct 1995 22:43:47 +0100 From: se@zpr.uni-koeln.de (Stefan Esser) To: Bruce Evans <bde@zeta.org.au> Cc: se@sysiphos.mi.uni-koeln.de Subject: Re: VLB Disk Controllers Message-ID: <199510072143.AA11757@Sysiphos> In-Reply-To: Bruce Evans <bde@zeta.org.au> "Re: VLB Disk Controllers" (Oct 8, 7:15)
next in thread | previous in thread | raw e-mail | index | archive | help
On Oct 8, 7:15, Bruce Evans wrote: } That's not saying much. An IDE controller has a much lower command } overhead than the buslogic: } } Buslogic BT44C on 486DX2/66 VLB TOSHIBA MK537FB (slow disk): } Output for disklatency /dev/rsd0: } Command overhead is 4741 usec (time_4096 = 5164, time_8192 = 5586) } transfer speed is 9.6955e+06 bytes/sec } } Buslogic BT44C on 486DX2/66 VLB (QUANTUM XP34301 (fast disk): } output for disklatency /dev/rsd1: } Command overhead is 3968 usec (time_4096 = 4295, time_8192 = 4622) } transfer speed is 1.25286e+07 bytes/sec } } Cheap IDE on 486DX/33 ISA SAMSUNG SHD-3212A (slow disk): } output for disklatency /dev/rwd0: } Command overhead is 573 usec (time_4096 = 2830, time_8192 = 5087) } transfer speed is 1.81489e+06 bytes/sec } } A high command overhead causes slow file system operations for } everything except large i/o's. } } What are the command overheads of other popular controllers? NCR 53c810 (driven by a 486DX2/66): Command overhead is 751 usec (time_4096 = 1216, time_8192 = 1682) transfer speed is 8.79954e+06 bytes/sec Seems that even at 4KB, the NCR is a lot faster than an IDE controller :) Let's see: IDE: 512/1815890 s + 573 us = 855 us NCR: 512/8799540 s + 751 us = 809 us Seems the NCR is faster on 512 byte transfers. Now I guess this is not really a "large i/o" :) Regards, STefan -- Stefan Esser, Zentrum fuer Paralleles Rechnen Tel: +49 221 4706021 Universitaet zu Koeln, Weyertal 80, 50931 Koeln FAX: +49 221 4705160 ============================================================================== http://www.zpr.uni-koeln.de/staff/esser/esser.html <se@ZPR.Uni-Koeln.DE>
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199510072143.AA11757>