ahd(4) poor performance

[Justin T. Gibbs]

dd is synchronous.  You'd need to aggregate the throughput of several dd 
operations
to see the impact of overlapped commands.

--
Justin

--On Friday, June 23, 2006 6:52 PM +0300 Volodymyr Kostyrko 
<arcade at synergetica.dn.ua> wrote:

> Justin T. Gibbs ?????:
>> --On Thursday, June 22, 2006 12:16 AM +0300 Volodymyr Kostyrko
>> <arcade at synergetica.dn.ua> wrote:
>>
>>> Hi all.
>>>
>>>    I have:
>>>
>>> ahd0: <Adaptec (Dell OEM) 39320 Ultra320 SCSI adapter> port
>>> 0xdc00-0xdcff,0xd800-0xd8ff mem 0xdfbfe000-0xdfbfffff irq 66 at device
>>> 7.0 on pci3
>>> ahd0: [GIANT-LOCKED]
>>> aic7902: Ultra320 Wide Channel A, SCSI Id=7, PCI-X 101-133Mhz, 512 SCBs
>>> ahd1: <Adaptec (Dell OEM) 39320 Ultra320 SCSI adapter> port
>>> 0xd400-0xd4ff,0xd000-0xd0ff mem 0xdfbfc000-0xdfbfdfff irq 67 at device
>>> 7.1 on pci3
>>> ahd1: [GIANT-LOCKED]
>>> aic7902: Ultra320 Wide Channel B, SCSI Id=7, PCI-X 101-133Mhz, 512 SCBs
>>>
>>>    Booting machine also results in:
>>>
>>> ahd0: Invalid Sequencer interrupt occurred.
>>
>> This error is benign.
>>
>> There have been issues reported with some recent Seagate drives and
>> large queue depths.  You may get better performance if you use camcontrol
>> to lower the queue depth to 63 or 32.  I believe that 32 is the default
>> used by Linux.
>>
>> --
>> Justin
>
>    Interesting.
>
>    By default I have the following:
>
> srv4# camcontrol tags 0:0 -v
> (pass1:ahd0:0:1:0): dev_openings  1
> (pass1:ahd0:0:1:0): dev_active    0
> (pass1:ahd0:0:1:0): devq_openings 1
> (pass1:ahd0:0:1:0): devq_queued   0
> (pass1:ahd0:0:1:0): held          0
> (pass1:ahd0:0:1:0): mintags       2
> (pass1:ahd0:0:1:0): maxtags       255
>
>    Raising this to higher values provides better perfomance:
>
> @1:
>
>  > dd if=/dev/zero of=somefile count=20480
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 1.114188 secs (9411123 bytes/sec)
>
> @2:
>
>  > dd if=/dev/zero of=somefile count=20480
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 0.402884 secs (26026747 bytes/sec)
>
>    Raising it further doesn't help anyway. And it still behaves not so
> fast as Linux.
>
> --
> [WBR], Arcade.
>