topic Re: pvcreate on an iSCSI connected disk in Operating System - HP-UX

pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 08:48:22 GMT

I see my disk when I do an ioscan -fnC disk but when I do a pvcreate on it, it returns nothing (/dev/dsk/c8t0d0 is my iSCSI connected disk). Any thoughts?

# ioscan -fnC disk
Class I H/W Path Driver S/W State H/W Type Description
==========================================================================
disk 0 0/0/1/1.2.0 sdisk CLAIMED DEVICE HP 36.4GST336753LC
/dev/dsk/c1t2d0 /dev/rdsk/c1t2d0
disk 1 0/0/2/0.2.0 sdisk CLAIMED DEVICE HP 36.4GST336753LC
/dev/dsk/c2t2d0 /dev/rdsk/c2t2d0
disk 2 0/0/2/1.2.0 sdisk CLAIMED DEVICE HP DVD-ROM 305
/dev/dsk/c3t2d0 /dev/rdsk/c3t2d0
disk 4 0/10/0/0.24.0.239.0.0.0 sdisk CLAIMED DEVICE DGC CX600WDR5
/dev/dsk/c7t0d0 /dev/rdsk/c7t0d0
disk 3 255/0/0.0.0.0 sdisk CLAIMED DEVICE DGC CX500WDR5
/dev/dsk/c8t0d0 /dev/rdsk/c8t0d0

Re: pvcreate on an iSCSI connected disk

Patrick Wallek — Mon, 22 Aug 2005 08:50:54 GMT

What do you mean "returns nothing"? Does it come back to the prompt? Do the pvcreate, then when it gets back to the unix prompt, do an 'echo $?' to see the return code. Is it 0 or 1 or something else?

What happens if you try a 'pvcreate -f /dev/rdsk/c8t0d0'?

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 08:53:24 GMT

I tried pvcreate and pvcreate -f. When I say it returns nothing, I mean it never brings me back to a prompt.

Re: pvcreate on an iSCSI connected disk

Pedro Cirne — Mon, 22 Aug 2005 09:01:42 GMT

Hi,

Post here the following:

#diskinfo /dev/rdsk/c8t0d0
#diskinfo /dev/rdsk/c8t0d0

May be those devices are the "gatekeepers"..or the LUNs are locked, or not "enabled"...

Enjoy :)

Pedro

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 09:03:02 GMT

# diskinfo /dev/rdsk/c8t0d0
SCSI describe of /dev/rdsk/c8t0d0:
vendor: DGC
product id: CX500WDR5
type: direct access
size: 10485760 Kbytes
bytes per sector: 512

Re: pvcreate on an iSCSI connected disk

Devender Khatana — Mon, 22 Aug 2005 09:03:05 GMT

Hi,

What does diskinfo report for this disk. The I/O to the disk can also bechecked by running dd on it.

Does dd goes fine?
What is the capacity of the disk?

HTH,
Devender

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 09:04:03 GMT

What is dd?

Re: pvcreate on an iSCSI connected disk

Devender Khatana — Mon, 22 Aug 2005 09:05:49 GMT

Hi,

dd is the command to copy data from one device to another. Man dd for details.

HTH,
Devender

Re: pvcreate on an iSCSI connected disk

Pedro Cirne — Mon, 22 Aug 2005 09:05:50 GMT

Hi,

I guess this is an EMC Disk Array, probably the LUN is read-only or locked, you will need EMC help on this .-)

Enjoy :)

Pedro

Re: pvcreate on an iSCSI connected disk

Devender Khatana — Mon, 22 Aug 2005 09:12:03 GMT

Hi,

You can find out if your system can read the disk or not using

dd if=/dev/dsk/c8t0d0 of=/dev/null bs=1024K

And wheather you can write it or not by

dd if=dev/zero of=dev/dsk/c8t0d0 bs=1024K

HTH,
Devender

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 09:13:19 GMT

# dd if=/dev/dsk/c8t0d0 of=/dev/null bs=1024K
dd: invalid number specification in option
# dd if=dev/zero of=dev/dsk/c8t0d0 bs=1024K
dd: invalid number specification in option

Re: pvcreate on an iSCSI connected disk

Pedro Cirne — Mon, 22 Aug 2005 09:16:05 GMT

Hi,

The LUN is locked or not enabled on the array side, I'm almost sure .-)

Enjoy :)

Pedro

Re: pvcreate on an iSCSI connected disk

Devender Khatana — Mon, 22 Aug 2005 09:16:22 GMT

Hi,

use k instead of K in the command.

HTH,
Devender

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 09:34:52 GMT

Well a pvcreate I had running for about 1/2 an hour finally completed successfully. Doesn't appear to be a lock LUN, but the time it took to complete has me a bit concerned.

Re: pvcreate on an iSCSI connected disk

Pedro Cirne — Mon, 22 Aug 2005 09:38:51 GMT

Hi Scott,

If performance is too low, you should check if write cache is enabled on the disk array side, it's strange that it tooks half an our to do a pvreate...

Pedro

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 09:49:53 GMT

Yes, write cache and read cache is enabled on the CX500

Re: pvcreate on an iSCSI connected disk

Devender Khatana — Mon, 22 Aug 2005 09:50:45 GMT

Hi Scott,

This indicates some problem if the pvcreate tokk so long. I would suggest reading the complete disk with dd and see how much it takes. It shall indicate the I/O rate as well. Another thing you could try is to create vg & file system on the disk and then mount it. Then copy some existing file system data to disk and see transfer rate.

#find /var -name "*" -print |cpio -pdmv /new_mount-point

Where your new file system is mounted at /new_mount-point.

But lokking at the symptoms I do not know how much time it will take to create the file system.

I suppose you use command line pvcreate only and not initialized media somehow which can run mediainit on the disk and could take this much time.

HTH,
Devender

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Mon, 22 Aug 2005 13:14:33 GMT

Devender,

I ran the dd right after you posted that I should use a lower case k instead of an upper case K. It still hasn't returned to a prompt.

Scott

Re: pvcreate on an iSCSI connected disk

Devender Khatana — Wed, 24 Aug 2005 10:09:58 GMT

Hi,

As it is reading the whole disk it may take a while. Reading a whole 10GB LUN could take a max. of 15-20 minutes. How long it took in your case to come back to a prompt?

Is there any improvement on this?

Regards,
Devender

Re: pvcreate on an iSCSI connected disk

Scott Frye_1 — Wed, 24 Aug 2005 11:53:39 GMT

pvcreate took 30 minutes on 10 gig lun. EMC said they do not support iSCSI with HP-UX... has anyone done this before?

Scott