Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!sdd.hp.com!apollo!goykhman_a
From: goykhman_a@apollo.HP.COM (Alex Goykhman)
Newsgroups: comp.periphs.scsi
Subject: Re: Low disk throughput on Xenix 2.3.2/
Message-ID: <5085948c.20b6d@apollo.HP.COM>
Date: 22 Mar 91 19:51:00 GMT
Sender: root@apollo.HP.COM
Reply-To: goykhman_a@apollo.HP.COM (Alex Goykhman)
Organization: Hewlett-Packard Apollo Division - Chelmsford, MA
Lines: 62

In article <1991Mar21.055200.29525@simasd.uucp> jcurtis@simasd.uucp (Jay Curtis) writes:
>In article <283400078@adaptx1> neese@adaptx1.UUCP writes:
>>
>>>	I am having a problem with SCO Xenix 2.3.2GT and very low disk
>>>transfer rates.  Here is my configuration:
>(stuff deleted)
>
>>>With this config, I am only able to get 124K Bytes/sec. throughput under
>>>Xenix.  Under Dos I get 496 K Bytes/sec.  Under ISC Unix, similar rates
>>>to Dos.  Is there a known problem with the scsi drivers under Xenix?
>>>Why would throughput be so low?  Running the same config except for the
>>>drives and controller (substitue in a wd1003 controller and Maxtor 2190)
>>>gave me double the disk throughput.  Why???
>>
>>Get the xnx252 driver from SCO or adaptex.  You will see a performance gain.
>>You could also check to see of the read ahead cache is enabled in the drive
>>via SCSICNTL.  If it isn't, try enabling it.
>>
>I am sorry.  I forgot to tell you that the 124K was with xnx252
>installed!  Also the read ahead cache is enabled.  I am in ASYNC mode as
>the other drive on the host adapter does not support SYNC transfers.
>When I tried enabling SYNC on the host adapter, the system would hang on
>bootup.
>
>Any other ideas?  This is making me crazy!


    Depending on the drive, ASYNC can cut the throughput by as much as 50%.
    Disconnect the second drive, and try the first one in the SYNC mode.

    PIO instead of DMA can lower throughput substantially, but not to 124Kb/sec.

    Finally, the drive have been formatted (FORMAT UNIT) with a ridiculously
    high interleave.

>>			Roy Neese
>>			Adaptec Senior SCSI Applications Engineer
>>			UUCP @  neese@adaptex
>>				uunet!cs.utexas.edu!utacfd!merch!adaptex!neese
>
>
>--Jay
>-- 
>Jay Curtis  
>jcurtis@baron.UUCP	
>{nosc;ncr-sd;ucsd;}!baron!jcurtis
>Of course my opinions are my own... Who would let me speak for them?!

    Alex Goykhman

P.S.  The systems hangs with both the SYNC and ASYNC drives because the driver
      does not set the transfer mode properly, i.e. BEFORE the first REQ of
      a DATA IN/OUT phase.  That should be easy to fix, so you might want to
      talk the developers. 

      496Kb/sec is a very low transfer rates, 124Mb/sec is laughable.  Those
      developers should be ashamed of that kind of SCSI driver.
      



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