Need a script to check Mirroring in consistencies

Febi881 · 11-24-2015, 09:33 AM

Dear Friends,

I was preparing a script to verify the mirroring consistencies on Linux servers. I was able to write a working one, but when I tested, I found a bug and right now I am running out of logic to fix it.

Set Up: Curretly we are using emc disks and disk name includes numbers 380 and 381 on a constant location in the name.

Eg: /dev/mpath/3600009700002957003801iet00010003
/dev/mpath/3600009700002957003811iet00010004

My script will grab 380 from mirror leg 0 and 381 from mirror leg 1
and if they are different then it will report a consistant mirror. Else it will report the issue and vice versa(in case of 381 on mirror leg 0 and 380 on leg 1).

My script is working fine when lvs and vgs having different names, But it is not, when we have same lv names on different vgs.

I have attached my script and a sample output of lvs -a -o +devices command output. Any suggestions are welcome to fix the issue.

MensaWater · 11-25-2015, 03:07 PM

On "lvs -a -o +devices " you could add specific VG so it does it only to the specific VG.

If you nested your existing commands within a larger loop you could do that dynamically and insure your script only seeing the LVs specific the VG the loop is currently processing. e.g.

Code:

for vg in $(vgs --noheadings |awk '{print $1}')
do lvs -a -o +devices $vg ... rest of line
   etc... (being sure to add the $vg to any lvs -a line you're doing)
done

I'm curious though. Are your EMC disks not already LUNs (RAID sets) defined within the EMC storage array itself? If so why do you need to mirror at host level? The main point of getting storage arrays is to let them handle the disk redundancy for you.

It sounds as if you're using mirroring in place of multipathing. The latter is designed to insure different paths to the same storage are combined. Since you're using mpath devices it appears you have multipathing turned on and if so each multipath device should be a combination of separate paths to the same disk from the storage array. Assuming that same disk is redundant within the array one mpath to each unique disk within the array should represent the various paths already so you shouldn't need to mirror 2 separate mpaths together.

Febi881 · 11-26-2015, 01:53 AM

Quote:

Originally Posted by MensaWater

On "lvs -a -o +devices " you could add specific VG so it does it only to the specific VG.

If you nested

Code:

for vg in $(vgs --noheadings |awk '{print $1}')
do lvs -a -o +devices $vg ... rest of line
   etc... (being sure to add the $vg to any lvs -a line you're doing)
done

Thank you so much for suggesting on this. I will modify my script accordingly and will test it.

Quote:

Originally Posted by MensaWater

I'm curious though. Are your EMC disks not already LUNs (RAID sets) defined within the EMC storage array itself? If so why do you need to mirror at host level? The main point of getting storage arrays is to let them handle the disk redundancy for you.

It sounds as if you're using mirroring in place of multipathing. The latter is designed to insure different paths to the same storage are combined. Since you're using mpath devices it appears you have multipathing turned on and if so each multipath device should be a combination of separate paths to the same disk from the storage array. Assuming that same disk is redundant within the array one mpath to each unique disk within the array should represent the various paths already so you shouldn't need to mirror 2 separate mpaths together.

These are old systems and set up has been done very long back. So no one want us co change anything on this. Yes I am completely agreeing with you on RAID part and most of the EMC storage clusters have been configured with that. We already recommended to use the RAID as a cost effective mechanism to avoid disk failures and they do not agree with that. Here, what my script is trying to do is nothing but to avoid the manual errors during mirror extensions like reattaching a combination of different disks from different data centres on same mirror leg.