[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-smp
Subject:    SCSI performance, Was: Motherboard recommendations
From:       Jakob Oestergaard <jakob () ostenfeld ! k-net ! dk>
Date:       1997-12-29 23:13:24
[Download RAW message or body]


On Mon, 29 Dec 1997, Christian Balzer wrote:

> What version of the driver do you use? And have you enabled at least
> FAST (10MB/s) transfers by setting the synchronous transfer frequency
> to 10 in the kernel config? With an 810 based card that's the most
> you'll get anyway.

I tried both the drivers that can work with the 810. I also tried enabling
Fast SCSI on the one driver where that's possible. That removed the
SLOW-SCSI messages but not the slowness of the array.

> Linear won't increase the speed, RAID-0 will, 

I am aware of that    :)

> but as Herbert wrote
> your narrow FAST SCSI bus will be overloaded by the 5 disks, either
> distribute them on more controllers or go for an Ultra SCSI one, like
> the 875 based ones. From the data I have about 3 Fireball STs will
> saturate the 10MB/s of FAST SCSI. 

Yes, but should saturation mean going to 5.5 Megs/sec. on a 10 MHz bus ? 

I find that strange, but I can accept it if you say it is so...

One fireball ST gives me approx. 5 Megs/sec. on large reads. The RAID-0
array gave me approx. 5.5 Megs/sec. I would have expected close to 10
Megs/sec. well aware of the fact that two or three disks could saturate
the bus.  But perhaps my expectations are simply unfair. I am no SCSI
guru. 


> Also make sure you you don't increase
> the MAX tagged commands over the default of 4, according to several
> discussions on the SCSI list the Fireballs will break around 7...

I thought that was for old fireballs only.

Anyway, I haven't overridden the default queue depth.


Thanks,

................................................................
: jakob@ostenfeld.dtu.dk  : And I see the elder races,         :
:.........................: putrid forms of man                :
:   Jakob Østergaard      : See him rise and claim the earth,  :
:        OZ9ABN           : his downfall is at hand.           :
:.........................:...........(Konkhra)................:

[prev in list] [next in list] [prev in thread] [next in thread]