Amanda-Users

Re: VXA-2 packet-loader issues -- a scsi question added

2005-02-14 16:37:52
Subject: Re: VXA-2 packet-loader issues -- a scsi question added
From: "James D. Freels" <freelsjd AT ornl DOT gov>
To: amanda <amanda-users AT amanda DOT org>
Date: Mon, 14 Feb 2005 16:31:05 -0500
this is consistent with what the Exabyte Tech support told me.  The tape library comes with scsi id 0 by default while the tape drive had an scsi id = 11.  Now how many bootable scsi drives have anything but scsi id=0.  So, there was a direct conflict.  I changed the scsi id=3 on the library and =6 for the tape drive to avoid any conflicts and compact the ids as much as possible.  The Exabyte tech support stated that it is idle to have the autoloader/driver as low as possible to gain good performance.  When he realized I had hard drives on the same scsi chain, he immediately recommended a separate scsi card.

My question is:  you have 15 devices available on a wide scsi card.  When will it ever get fully populated ?  I guess only if all the devices are the same (like 15 hard drives ?)

On Mon, 2005-02-14 at 16:11 -0500, Jon LaBadie wrote:
On Mon, Feb 14, 2005 at 03:55:31PM -0500, James D. Freels wrote:
> I have the new scsi card (an inexpensive LSILogic LSIU80ALVDB) that
> fixes the problems I was having.  So, the Exabyte tech support was
> correct and the great advice I got herein this mailing list also said
> "get a separate scsi card" !
...
> 
> On Mon, 2005-02-07 at 16:20 -0500, James D. Freels wrote:
> 
> > I am near positive I did not fry anything since everything is working
> > correctly except a sustained write to the tape.

I recently read an article on trouble shooting I/O performance.
Most was related to disk I/O, but one tiny piece caught my eye
and could be related.

The writer claimed that on a SCSI bus the lower ID numbers were given
precedence (priority?), the effect of which was felt during heavy usage.
Further, this effect could particularly be felt by tape drives with high
SCSI numbers.  During heavy total I/O on the bus they would lose their
ability to stream more easily than if they had lower ID's.

For those intimate with Miss SCSI, any comments?


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