hardware mirror & quorum

[mjos]

Hi,

We have a ia64 hp server BL860c, which is harware mirrored.
I want to know when it is hardware mirrored, does quorum come into play. I mean do we need disable quorum for the primary disk.


# sasmgr get_info -D /dev/sasd0 -q raid



Fri Mar 20 06:04:47 2009



---------- LOGICAL DRIVE 1 ----------



Raid Level : RAID 1

Volume sas address : 0x8ace538684c9ace

Device Special File : /dev/rdsk/c0t0d0

Raid State : OPTIMAL

Raid Status Flag : ENABLED

Raid Size : 139898

Rebuild Rate : 0.00 %

Rebuild Progress : 100.00 %



Participating Physical Drive(s) :



SAS Address Enc Bay Size(MB) Type State



0x5000c50006306fe5 1 2 140014 SECONDARY ONLINE

0x5000c50006337645 1 1 140014 PRIMARY ONLINE


# lvlnboot -v
Boot Definitions for Volume Group /dev/vg00:
Physical Volumes belonging in Root Volume Group:
/dev/dsk/c0t0d0s2 (0/2/1/0.0.0.0.0) -- Boot Disk
Boot: lvol1 on: /dev/dsk/c0t0d0s2
Root: lvol3 on: /dev/dsk/c0t0d0s2
Swap: lvol2 on: /dev/dsk/c0t0d0s2
Dump: lvol2 on: /dev/dsk/c0t0d0s2, 0

# efi_cp -d /dev/dsk/c0t0d0s1 -u /EFI/HPUX/AUTO /tmp/AUTO.pri
# cat /tmp/AUTO.pri
boot vmunix

[Ganesan R]

Hi,

No. quourm will not come into picture for hardware mirrored/raid disks.

From OS or LVM point of view it is just one disk which will be mirrored at array level.

[Steven E. Protter]

Shalom,

Hardware mirroring presents multiple disks to the system as 1 disk.

Only the presented disk counts toward the quorum.

SEP

[Torsten.]

Quorum means you need to have more than 50% of disks available in a VG in order to activate it.

With only 1 disk (this is how the OS see your hardware mirror) you have always 100% of disks.

[mjos]

Thanks,

If one of the disk go offline, will the server still come up with only boot vmunix & with only one disk.
In this case shouldnt the AUTO file need boot vmunix -lq

[Torsten.]

No, not needed.

Do an ioscan and you will see ONLY 1 disk.

Example

disk 1 0/4/1/0.0.0.0.0 sdisk CLAIMED DEVICE
HP IR Volume
/dev/dsk/c1t0d0 /dev/rdsk/c1t0d0
/dev/dsk/c1t0d0s1 /dev/rdsk/c1t0d0s1
/dev/dsk/c1t0d0s2 /dev/rdsk/c1t0d0s2
/dev/dsk/c1t0d0s3 /dev/rdsk/c1t0d0s3

[Torsten. · Accepted solution]

Sorry forgot to say - compare the ioscan with your sasmgr output:

Device Special File : /dev/rdsk/c1t0d0

A single device file for a single logical disk (Integrated RAID [IR] volume).

[mjos]

What if this disk crashes, will the server still come up with quorum activated.

Ioscan shown one disk but sasmgr shows two disks.

[Patrick Wallek]

Yes, sasmgr is showing 2 disks because there are 2 physical drives in the system.

HP-UX is seeing only 1 disk because you have set up a hardware mirror consisting of those 2 physical disks. This hardware mirror is presented to HP-UX as 1 logical disk.

If one of the physical disks fails, your system should still boot fine. The array card will know not to use the failed disk, only the good disk.

[Ganesan R]

Hi,

You are making yourself confused. Just understand the concept.

For array it is two disk. For server it is only one disk. Array will combine these two disks and shows to the server as only one disk. This is how raid is working

If one disk crashes, server has no way to know if one disk failed in the array. Still from the server one disk is visible.But at storage, will manage till the remaining one disk is alive. If both disk fails, array will report to the server that no disks are available.