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alternate links

himacs
Super Advisor

alternate links

Hi Admins,

I believe for alternate links controller number will be different and target and disk number will be same with primary link.

I want to know how alternamte links generating.Because in below ioscan output i cannot find any alternate links.

disk 98 0/3/1/0/4/0.1.1.0.0.0.0 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t0d0 /dev/rdsk/c10t0d0
disk 99 0/3/1/0/4/0.1.1.0.0.0.1 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t0d1 /dev/rdsk/c10t0d1
disk 100 0/3/1/0/4/0.1.1.0.0.2.0 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d0 /dev/rdsk/c10t2d0
disk 101 0/3/1/0/4/0.1.1.0.0.2.1 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d1 /dev/rdsk/c10t2d1
disk 102 0/3/1/0/4/0.1.1.0.0.2.2 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d2 /dev/rdsk/c10t2d2
disk 103 0/3/1/0/4/0.1.1.0.0.2.3 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d3 /dev/rdsk/c10t2d3
disk 104 0/3/1/0/4/0.1.1.0.0.2.4 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d4 /dev/rdsk/c10t2d4
disk 105 0/3/1/0/4/0.1.1.0.0.2.5 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d5 /dev/rdsk/c10t2d5
disk 106 0/3/1/0/4/0.1.1.0.0.2.6 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t2d6 /dev/rdsk/c10t2d6
disk 107 0/3/1/0/4/0.1.1.0.0.15.0 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t15d0 /dev/rdsk/c10t15d0
disk 108 0/3/1/0/4/0.1.1.0.0.15.1 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t15d1 /dev/rdsk/c10t15d1
disk 109 0/3/1/0/4/0.1.1.0.0.15.2 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c10t15d2 /dev/rdsk/c10t15d2
disk 2 0/4/1/0.0.0.2.0 sdisk CLAIMED DEVICE HP DG072A9BB7
/dev/dsk/c2t2d0 /dev/dsk/c2t2d0s2 /dev/rdsk/c2t2d0 /dev/rdsk/c2t2d0s2
/dev/dsk/c2t2d0s1 /dev/dsk/c2t2d0s3 /dev/rdsk/c2t2d0s1 /dev/rdsk/c2t2d0s3
disk 110 0/4/1/0.0.0.3.0 sdisk CLAIMED DEVICE HP DG072A9BB7
/dev/dsk/c2t3d0 /dev/dsk/c2t3d0s2 /dev/rdsk/c2t3d0 /dev/rdsk/c2t3d0s2
/dev/dsk/c2t3d0s1 /dev/dsk/c2t3d0s3 /dev/rdsk/c2t3d0s1 /dev/rdsk/c2t3d0s3
disk 111 0/4/1/0.0.0.4.0 sdisk CLAIMED DEVICE HP DG146BB976
/dev/dsk/c2t4d0 /dev/rdsk/c2t4d0


Moreover some device file shows size in MBs.

diskinfo /dev/rdsk/c2t2d0s1
SCSI describe of /dev/rdsk/c2t2d0s1:
vendor: HP
product id: DG072A9BB7
type: direct access
size: 512000 Kbytes
bytes per sector: 512


Please suggest on this..

Regards
himacs
8 REPLIES
Johnson Punniyalingam
Honored Contributor

Re: alternate links

You can start with "powermt" command

powermt display dev=all


Also check below thread for more explantion on alternative links,

http://forums13.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1265706437764+28353475&threadId=995304
Problems are common to all, but attitude makes the difference
BUPA IS
Respected Contributor

Re: alternate links

Hello,
The alternate links are shown using different control unit numbers with the same device and target numbers.
When working with EMC arrays you can map the disk id to the device file using the EMC supplied inq command which helps
sort out which disk is which.
./inq.HP
-----------------------------------------------------------------------------
DEVICE :VEND :PROD :REV :SER NUM :CAP(kb)
-----------------------------------------------------------------------------

/dev/rdsk/c14t0d0 :EMC :SYMMETRIX :5671 :55160000 : 23040
/dev/rdsk/c14t0d1 :EMC :SYMMETRIX :5671 :556F0000 :8923200
...............

/dev/rdsk/c16t0d1 :EMC :SYMMETRIX :5671 :556F0000 :8923200

The serial number is unique for the LUN in
question .
Note that the first disk is very small this is a gate keeper device for the array and does not store any data.
diskinfo /dev/rdsk/c14t0d0
SCSI describe of /dev/rdsk/c14t0d0:
vendor: EMC
product id: SYMMETRIX
type: direct access
size: 23040 Kbytes
bytes per sector: 512
You will only see alternate links if you have dual paths defined in the emc control units and you have mapped them in your SAN zones, usually down seperate fibre channel cards.
Mike
Help is out there always!!!!!
himacs
Super Advisor

Re: alternate links

HI ,

Thanks for your responses.In ioscan output i have not found alternate links to internal HP links.Is ther any way to create the same..

I believe max 8 alt links we can create.

I heard that If primary links fails I/O will use alternate links for its operation.So in my case whats the solution since there are no alternate links found.

Regards
himacs

BUPA IS
Respected Contributor

Re: alternate links

hello
In general the internal disks do not have alternate links. In some models they have seperate disk controllers for each disk or disk pair so by mirroring the internal disks you remove the single point of failure.
Which model is your system ?
Mike
Help is out there always!!!!!
bobsam
Advisor

Re: alternate links

Hi Himacs,

Generally in hp storages after lun presenting we will intall securepath on servers and by using autopath command it will show the all paths. You can select any of this path for VG creation and remaining path will act as alternate path.

Pls check this.
saran2010
Occasional Advisor

Re: alternate links

The reason why some of the disk size shows in MB is,

diskinfo /dev/rdsk/c2t2d0s1
SCSI describe of /dev/rdsk/c2t2d0s1:

c2t2d0s1 is not a physcical disk, it is an EFI partition in Itanium boot disk.

this partion will be normally in MBs

Thanks

Saravanan
Torsten.
Acclaimed Contributor

Re: alternate links

As said, this is not disk, but the EFI boot partition

diskinfo /dev/rdsk/c2t2d0s1
SCSI describe of /dev/rdsk/c2t2d0s1:
vendor: HP
product id: DG072A9BB7
type: direct access
size: 512000 Kbytes
bytes per sector: 512



This is 500MB by default.

Usually internal disks have only 1 (primary) link, no alternates at all.

Hope this helps!
Regards
Torsten.

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saran2010
Occasional Advisor

Re: alternate links

If you are using 11.v3 means this command will help

ioscan -m dsf

ioscan -m dsf /dev/dsk/


Thanks

saravanan