topic Re: FC60 Disk Array in Disk Enclosures

FC60 Disk Array

Michael T. Harding — Tue, 19 Nov 2002 16:51:15 GMT

I have an L class server connected to an FC60 Disk Array. I have 2 luns configured and can see this when doing an amdsp -l (Display Luns)
when I do an ioscan on the disks I can see the luns as eg c9t0d0 and c9t0d1. If I do an diskinfo /dev/rdsk/c9t0d0 the size of the lun is returned. This I am happy with but I am confused about the ioscan as it returns disk information eg c9t2d0 c9t3d0. When I do a diskinfo of the devices it returns 0 size
vendor: HP
product id: A5277A
type: direct access
size: 0 Kbytes
bytes per sector: 0

Also on the ioscan there is a device c9t3d7 which relates to HP Universal Xport.

Can anyone help?

Re: FC60 Disk Array

Bill McNAMARA_1 — Tue, 19 Nov 2002 16:55:54 GMT

notice thqt the t field increases.
When you have luns numbered greater then 7, ( 3 bits) the 8th lun will be 1000 ie t+1 d0
The virtual target shows up in the ioscan.

Have a look in the storage forums for more on this.

Later,
Bill

Re: FC60 Disk Array

melvyn burnard — Tue, 19 Nov 2002 18:05:03 GMT

The FC60 seems to do this, but why I do not know.
I am moving this to the Disk array forum to see if you can get a better answer there

Re: FC60 Disk Array

Vincent Fleming — Tue, 19 Nov 2002 19:04:52 GMT

I'm much more familiar with the newer HP arrays, but I believe the FC60 has this same feature in common with the newer ones...

LUN 0 is a management interface - it should be zero length in size. User LUNs (ones you create) are LUN 1 thru LUN n (128? it depends on the array). Most HP arrays have this LUN 0 management LUN.

Examples of disk arrays with similar features - EMA (HSG80-based storage), EVA (HSV110), and XP arrays. The VA uses a LUN 0 for the same purpose, but it has size (usually small).

Perhaps someone who has an FC60 and is really familiar with it can confirm this.

Good luck!

Re: FC60 Disk Array

Eugeny Brychkov — Tue, 19 Nov 2002 20:40:30 GMT

Michael,
this is normal and these 'phantom LUNs' should be present because they create LUN 0 of target (SCSI Id). Example: LUN #12 = Id1+LUN4. To access this LUN you should have 'initiator' for this Id and it is Id1 LUN0. If you'll create this LUN physically in the FC60 then 'phantom' will be replaced by this 'real' LUN (so you'll see its non-zero size)
Eugeny

Re: FC60 Disk Array

Michael T. Harding — Wed, 20 Nov 2002 09:44:17 GMT

Many Thanks for your replies.
I only have 2 luns when looking at amdsp -l 0 and 1.
Output from ioscan
disk 18 0/3/0/0.8.0.5.0.0.0 sdisk CLAIMED DEVICE HP A5277A
dev/dsk/c9t0d0 /dev/rdsk/c9t0d0
Lun 0 53gb

disk 19 0/3/0/0.8.0.5.0.0.1 sdisk CLAIMED DEVICE HP A5277A
/dev/dsk/c9t0d1 /dev/rdsk/c9t0d1
Lun 1 17gb

disk 20 0/3/0/0.8.0.5.0.1.0 sdisk CLAIMED DEVICE HP A5277A
dev/dsk/c9t1d0 /dev/rdsk/c9t1d0
0 kbytes

disk 21 0/3/0/0.8.0.5.0.2.0 sdisk CLAIMED DEVICE HP A5277A
/dev/dsk/c9t2d0 /dev/rdsk/c9t2d0
0 kbytes

disk 22 0/3/0/0.8.0.5.0.3.0 sdisk CLAIMED DEVICE HP A5277A
/dev/dsk/c9t3d0 /dev/rdsk/c9t3d0
0 kbytes

disk 23 0/3/0/0.8.0.5.0.3.7 sdisk CLAIMED DEVICE HP Universal Xport
/dev/dsk/c9t3d7 /dev/rdsk/c9t3d7
size: 20480 Kbytes

Looks like the management lun was not setup as lun 0.

Re: FC60 Disk Array

Insu Kim — Wed, 20 Nov 2002 15:46:37 GMT

HP-UX uses 3 bit to address disk array LUNs.
With this limit, HP-UX can see only 8 LUNs (2^3) for a target.
AutoRAID 12H would be a good example for this.
In AutoRAID 12H, the maximum number of LUNs that can be created was 8.

A new type of addressing is used with FC60 in order to withdraw this restriction called "Volume Set Addressing(VSA)".
VSA is an enhancement that increases the number of LUNs that can be addressed on a fiber channel disk array.
The FC60 requires that 32LUNs(0-31) be addressable.
To implement VSA, the fiber channel driver creates "four virtual SCSI busess", each capable of supporting up to eight LUNs.

The virtual SCSI bus is identified by the next-to-last segment of the hardware path.
In your case, four virtual SCSI bus are as follows.
0/3/0/0.8.0.5.0.0.0 (LUN 0 through 7)
0/3/0/0.8.0.5.0.1.0 (LUN 8 through 15)
0/3/0/0.8.0.5.0.2.0 (LUN16 through 23)
0/3/0/0.8.0.5.0.3.0 (LUN24 through 31)

The virtual SCSI bus will have device files and their size would be zero only if the first LUN on each virtual SCSI bus is not configured.

Based on your posting,
LUN0 and LUN1 would be LUNs in use and the others such as c9t1d0, c9t2d0, c9t3d0 are virtual SCSI busess for the disk array.

At this stage, you have only 2 LUNs called c9t0d0, c9t0d1.
Let's say that you create 7 LUNs more (Total LUNs : 9).
These are shown as c9t0d0, c9t0d1, c9t0d2, c9t0d3, c9t0d4, c9t0d5, c9t0d6, c9t0d7, c9t1d0.
At this moment, LUN 0 on virtual SCSI bus 1 (c9t1d0) would be LUN8 on the disk array.

Hope this helps,