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Date:      Sat, 9 Feb 2002 13:43:10 +0200
From:      Vallo Kallaste <kalts@estpak.ee>
To:        Craig Stratton <craig@avnet.co.uk>
Cc:        freebsd-bugs@freebsd.org
Subject:   Re: kern/34711: frequent system stall under moderate scsi load
Message-ID:  <20020209114310.GB6700@myhakas.estpak.ee>
In-Reply-To: <200202081440.g18Ee3f61695@freefall.freebsd.org>
References:  <200202081440.g18Ee3f61695@freefall.freebsd.org>

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On Fri, Feb 08, 2002 at 06:40:03AM -0800, Craig Stratton <craig@avnet.co.uk> wrote:

> The following reply was made to PR kern/34711; it has been noted by GNATS.
> 
> From: "Craig Stratton" <craig@avnet.co.uk>
> To: "David Malone" <dwmalone@maths.tcd.ie>
> Cc: <freebsd-gnats-submit@freebsd.org>
> Subject: Re: kern/34711: frequent system stall under moderate scsi load 
> Date: Fri, 8 Feb 2002 14:34:03 -0000
> 
>   David,
>  
>  i'm not sure if the system time is usual or not. But it sounds like it
>  shouldn't be...
>  
>  It could be a memory problem, as you say, because it only has 64MB, but the
>  previous system i ran exactly the same things on only had 16MB on a P75 IDE
>  and had no problems. Uptime over 500 days before replacement with "better"
>  hardware :-|
>  Can't remember what release it was on though. Slightly earlier i believe.
>  
>  There is never anything logged anywhere whenever the system stalls or hangs,
>  which is frustrating...
>  
>  I think the problem is certainly in the swapping/disk access area, as all
>  disk operations seem to take a while. When it hangs, i can get ssh login,
>  but no shell until it comes back.
>  
>  I was looking over how to upgrade "in situ" last night, but was too tired to
>  take it in.
>  Can you advise how i would go about bringing up to date online with no
>  physical access to the machine ? (other than carefully .. ;-) )
>  
>  The most i do normally is install from scratch, and add/configure
>  software/applications....
>  
>  ahc0: <Adaptec 2940 Ultra SCSI adapter> port 0x6000-0x60ff mem
>  0xe4000000-0xe4000fff irq 10 at device 9.0 on pci0
>  ahc0: aic7880 Wide Channel A, SCSI Id=7, 16/255 SCBs
>  pci0: <S3 Trio graphics accelerator> at 10.0 irq 9
>  
>  da1 at ahc0 bus 0 target 1 lun 0
>  da1: <QUANTUM FIREBALL ST4.3S 0F0C> Fixed Direct Access SCSI-2 device
>  da1: 10.000MB/s transfers (10.000MHz, offset 15), Tagged Queueing Enabled
>  da1: 4136MB (8471232 512 byte sectors: 255H 63S/T 527C)
>  da0 at ahc0 bus 0 target 0 lun 0
>  da0: <QUANTUM FIREBALL ST4.3S 0F0C> Fixed Direct Access SCSI-2 device
>  da0: 10.000MB/s transfers (10.000MHz, offset 15), Tagged Queueing Enabled
>  da0: 4136MB (8471232 512 byte sectors: 255H 63S/T 527C)

Those SCSI Quantum Fireball ST disks are _really_ slow. I've had one
some years ago and never got more than 2.5-3MB/s _sequential_ read
throughput, it didn't matter was it under FreeBSD or NT 4.0. Random
access throughput is worse.. 
-- 

Vallo Kallaste
kalts@estpak.ee

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