SCSI Priorities.

[Russ Hancock_1]

Hi all.

What is the ideal SCSI ID order for a K400, with respect to system performance ? And how do you tell what the ID's are currently set to?

I've attached an ioscan, incase that helps?

Cheers
Russ.

[Helen French]

Hi,

Check this out:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x83c928e43106d6118ff40090279cd0f9,00.html

HTH,
Shiju

[Sanjay_6]

Hi Russ,

The SCSI order is 7-0, 15-8 i think. if the path to a disk is shown as 10/4/12.2.0 the scsi id of the disk is 2 and the SCSI path it is connected to is 10/4/12.

If the path is shown as 10/4/12.2.1

the SCSI id of the lun is 1, the scsi id of the controller is 2 and the scsi path it is connected to is 10/4/12

Hope this helps.

Regds

[Uday_S_Ankolekar]

Hi,
10/0.6.0 6 is the SCSI ID
10/0.7.0 7 is the SCSI ID and so on.

10/0 is the bus address

-USA..

[Sanjay_6]

Hi Russ,

The above mentioned scsi address priorities were for a FWD SCSI bus. For a SE SCSI the order is 7-0 only. Also take a look at the threads below for more info,

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=005ac9b20ca9f8a089/screen=ckiDisplayDocument?docId=200000007950892

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=005ac9b20ca9f8a089/screen=ckiDisplayDocument?docId=200000046785420

Hope this helps.

Regds

[A. Clay Stephenson]

Hi Russ:

The priorities are in the order highest to lowest: 7,6,5,4,3,2,1,0,15,14,13,12,11,10,9,8

Any controller on the bus (there can be more than one) should have the highest priorities.
In general, next come magnetic disks followed by CD-ROM's and tape drives.

Beyond that, you are going to find that it doesn't make much difference who gets what SCSI ID. Of much greater importance, is that as many separate buses are used to spread the I/O over as many channel as possible. Sar and Glance can be used to identify hot-spots. The
idea is to move the most active disks/filesystems to less active disks/filesystems.

Regards, Clay

[Helen French]

Hi again,

1)Normally, the priority level is from '7 to 0' and fm '15 to 8'.
2)Here SCSI id '7' will be reserved for the controller (high priority).
3)Then HP suggest setting id '6' for the root disk.
4)The backup device is set to id '0' normally and the CD Drive to id '4'.

HTH,
Shiju

[Russ Hancock_1]

How can I tell what the ID of the SCSI cards are? We have recently added a Wide SCSI card, alongside the internal FastWide card.

Although the Description says ID=7 is this the case really? and what ID should the internal FastWide card live at?

(node02) / # ioscan -fnC ext_bus
Class I H/W Path Driver S/W State H/W Type Description
===================================================================
ext_bus 0 10/0 c720 CLAIMED INTERFACE GSC built-in Fast/Wide SCSI Interface
ext_bus 3 10/4/12 scsi3 CLAIMED INTERFACE HP 28696A - Wide SCSI ID=7
ext_bus 2 10/12/0 CentIf CLAIMED INTERFACE Built-in Parallel Interface
/dev/c2t0d0_lp
ext_bus 1 10/12/5 c720 CLAIMED INTERFACE Built-in SCSI

[Geno Church]

The card you added should have scsi switch settings that you can modify on the card itself. But scsi id7 for that card (controller) should be fine. Now if you had two boxes in a service guard environment (2 boxes identical) then you would probably want to make one of the cards id 6, that way no conflicts. But the way you have it set up you should be fine. Just don't assign anything else as id 7 on that scsi chain.

Geno-HP

[Helen French]

Hi Russ,

I think you are bit confused with SCSI id and I/O channel.

From the ioscan output, it is confirmed that the built-in card and the new Wide SCSI card are on different I/O channel or bus. '10/0' is the Controller hardware address of the built-in card. '10/4/12' is the address of the new Wide Contoller.

Thus, if a HDD is connected to the new Wide SCSI card, it will be addressed like -10/4/12/5.0 (if the HDD id is 5). And whatever devices connected to built-in card will start with 10/0/X/X.0

HTH,
Shiju

[Sanjay_6]

Hi Russ,

Take a look at this from the ioscan output attached by you,

ctl 0 10/0.7.0 sctl CLAIMED DEVICE Initiator
/dev/rscsi/c0t7d0

Here the scsi id of the controller is 7. (10/0.7.0)

Hope this helps.

Regds

[Darrell Allen]

Hi Russ,

ioscan -fnkC ctl will list your controllers like:
ctl 0 0/0/1/0.7.0 sctl CLAIMED DEVICE Initiator
/dev/rscsi/c0t7d0

Note the 7 in c0t7d0 is the scsi id as well as the 7 in 0/0/1/0.7.0

Darrell

[Russ Hancock_1]

Thanks Chaps.

I'm starting to get the hang of it now.... And yes I was confused!!

One final thing.
Will changing SCSI priorities really make much difference??
Particularly, with my root logical volume vg00
consisting of 2 disks one at ID6 the other way down at ID9???

Thanks again,
Russ