topic Re: Mirror in Operating System - HP-UX

Mirror

JUP — Mon, 24 Jul 2000 00:26:03 GMT

I mirrored the drive /dev/dsk/c0t14d0 to /dev/dsk/c0t15d0 using:
"lvextend -m 1 /dev/vg01/data1 /dev/dsk/c0t15d0" - no problems, all seems to work OK.
My question is how do I check to see if the mirroring is working OK. I tried mounting the /dev/dsk/c0t15d0 device and the reply was "unrecognized file system". Can I check the data on the mirrored drive to make sure it is mirroring or do I just trust it is ?

Re: Mirror

exec — Mon, 24 Jul 2000 05:09:22 GMT

You can use:
#lvdisplay -v /dev/vg01/data1
then u can find the information are different from lv not mirrored.

Another way is:
#dd if=/dev/vg01/rdata1 of=/dev/null bs=64k

U should see the two disks blinking at same frequency.

Re: Mirror

Andreas Voss — Mon, 24 Jul 2000 05:36:12 GMT

Hi,

you cannot mount /dev/dsk/c0t15d0 because you are using LVM and mounting disk device is not supported.
With lvdisplay -v /dev/vg01/data1 you can see if mirroring is working:
The output looks like:
--- Logical volumes ---
LV Name /dev/vg01/data1
VG Name /dev/vg01
LV Permission read/write
LV Status available/syncd
Mirror copies 1
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 40
Current LE 10
Allocated PE 20
Stripes 0
Stripe Size (Kbytes) 0
Bad block on
Allocation strict
IO Timeout (Seconds) default

--- Distribution of logical volume ---
PV Name LE on PV PE on PV
/dev/dsk/c0t14d0 10 10
/dev/dsk/c0t15d0 10 10

--- Logical extents ---
LE PV1 PE1 Status 1 PV2 PE2 Status 2
0000 /dev/dsk/c0t14d0 0171 current /dev/dsk/c0t15d0 0171 current

As you see there are two PV's (physical volumes) for each LE (logical extend).
If there are all LE on both PE your mirroring is working correct.

Regards

Andrew

Re: Mirror

warghade — Mon, 24 Jul 2000 05:40:46 GMT

Use the following command to check,

# lvdisplay /dev/vg01/data1
--- Logical volumes ---
LV Name /dev/vg01/data1
VG Name /dev/vg01
LV Permission read/write
LV Status available/syncd
Mirror copies 1

If the above entry "Mirror copies 1" is there means ur /dev/vg01/data1 is mirrored.
To check if the mirroring is working OK or not, write one file (eg. test) on /dev/vg01/data1 and save it then just unplug the disk on which vg01 is configured then try to open the same file (# vi test)
If the file opens it means mirroring is working OK.

I think this solves ur problem, good luck!

Re: Mirror

JUP — Mon, 24 Jul 2000 06:10:08 GMT

Thanks everyone.
I'm feeling confident all is OK now.

Re: Mirror

Dave Wherry — Mon, 24 Jul 2000 13:14:59 GMT

You can mount the mirror copy. First you need to use the lvsplit command to split off the mirror copy and then that can be mounted.
There is a pretty good document on the ITRC that covers this. The document ID is X1401978. It is about booting from a mirrored/split environment. You can use most of it for any volume.

Re: Mirror

N. Balasubrahmanian — Tue, 25 Jul 2000 06:13:17 GMT

You can also do a lvsplit. This will create logical volume say lvol1b. You can mount this lv and see if your data is getting updated properly. Then do an lvmerge. Take care, this is a dangerous command. Pls. go through the command syntax before executing this one. It can mirror the reverse way causing data loss.

Re: Mirror

N. Balasubrahmanian — Tue, 25 Jul 2000 06:13:58 GMT