Networker

[Networker] SCSI problems -- How many drives to a bus?

2004-01-09 12:35:14
Subject: [Networker] SCSI problems -- How many drives to a bus?
From: George Sinclair <George.Sinclair AT NOAA DOT GOV>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Fri, 9 Jan 2004 12:36:01 -0500
Hi,

We have a Storagetek L80 tape library with 4 LTO drives. We've been
seeing a lot of SCSI problems on the host. Host is a storage node
running RedHat Linux. I end up rebooting this host about once a week
because the /etc/LGTOuscsi/inquire utility fails to see the picker
device. This is really annoying. We finally moved the storage node to
another, more powerful Linux box with more buses, etc. Same problem
there!!! The first clue is the "read open error, Device or resource
busy" message that appears next to the affected device in the devices
section of the nwadmin window. Often, a backup will be running when the
host loses communication to the picker.

We have the robot on its own separate bus and all 4 drives share a bus.
Max sessions per device is set to 5. We're running 6.1.1 under Solaris
primary server. Should also note that we do have an ATL SDLT tape
library running on there, too. Its picker, and two drives all share same
bus, but this bus is its boss and does not share anything with the L80.
So, we have three Adpactec cards: one for ATL, one for L80 picker and
one for L80 LTO drives (dual channel Adapctec cards).

I'm wondering if we have too many LTO drives on the bus? Could this
cause these SCSI problems? Maybe better to have no more than two drives
per bus? Someone suggested that we get the picker on its own bus which
we recently did but that didn't fix it. I'm beginning to think that
there's something wrong with the Storage Tek library and maybe it's time
to have Storage Tek come look at it. Maybe we should get a temp license
for another storage node and move the ATL over there so we only have one
library on this host? Guess it would be easier to troubleshoot, but
seems silly to have to do that. NO reason we should not be able to run
two libraries, and the thing is is that the ATL libary never gives us
any problems. I never see these "read open error ..." messages on there.
Hmm ....

Any thoughts?

Thanks.

George

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