topic Re: Disk Mirroring in Operating System - HP-UX

Disk Mirroring

TMcB — Tue, 12 Feb 2002 11:48:39 GMT

Hi folks

I'm trying to understand MirrorDisk at the moment.

We have the following :
- 2 internal 8GB disks and
- 8 external 17GB disks
--------------------------------------------
Mbytes Physical Logical
Name Available Volumes Volumes
---------------------------------------------
vg00 984 of 8672 1 13
vg01 5932 of 8676 1 3
cpdb1 4568 of 17360 1 3
vgsgm01 11216 of 17360 1 3
vgsgm03 11216 of 17360 1 3
vgsgm04 11216 of 17360 1 3
vgsgm05 11216 of 17360 1 3
vgsgm06 11216 of 17360 1 3
vgsgm07 13264 of 17360 1 2
vgsgm02 11216 of 17360 1 3

At the very least, I would like to mirror the boot disk.
However, all our disks have something on them.
The external disks have over 10GB free on each one - is is possible to use this space for mirroring??

Thanks.

Re: Disk Mirroring

Joseph Chakkery — Tue, 12 Feb 2002 11:59:05 GMT

Hello,

I think u don't have much data on ur vg01 volume group. free up this disk by transferring data to any other volume group (other than vg00) by creating same mount points. Add this disk to vg00.
Do the following

Pvcreate ???B (-f for force if file system exists) /dev/rdsk/c?t?d?Vgextend /dev/vg00 /dev/dsk/c?t?d?Mkboot /dev/rdsk/c ?t ?d ?
Mkboot ???a ?? hpu( ;0)/stand/vmunix??? /dev/rdsk/c?t?d?

Lvextend ???m 1 /dev/vg00/lvol1 /dev/dsk/c?t?d?Same for all other volume to be mirrorLvlnboot ???R

Hope this helps.

Regards
Joe.

Re: Disk Mirroring

TMcB — Tue, 12 Feb 2002 12:04:23 GMT

Thanks for the reply

VG01 is the other internal disk - would it not be preferable to mirror to one of the external disks?

Do I understand you right -
whatever I decide to mirror, I have to add another disk to that volume gourp and mirror to the other disk??

Thanks

Re: Disk Mirroring

Joseph Chakkery — Tue, 12 Feb 2002 12:13:32 GMT

U r right Terry. The mirror should be on another disk so that when ever first disk fails u can get the data from the mirrored disk.

Regards
Joe.

Re: Disk Mirroring

John Palmer — Tue, 12 Feb 2002 13:12:05 GMT

Ideally, you should mirror similar sized disks and in order to be as resililient as possible, the disks should be connected by different controllers.

In your situation it would make best sense to use the two 8Gb disks as your mirrored root disks. If your server is one of the later types e.g. L or N class (or whatever they're called now) then there are two seperate internal SCSI channels for resilience (and performance).

You haven't got enough spare diskspace to mirror everything but plenty in order to mirror the boot disk. You'd have to relocate the data from your vg01 disk, remove vg01, then follow standard procedures for mirroring the boot disk. I presume that you have Mirrordisk installed?

Regards,
John

Re: Disk Mirroring

Sanjay_6 — Tue, 12 Feb 2002 13:39:54 GMT

Hi Terry,

For mirroring, you need to add that disk to the VG for which you want to do the mirroring. Say you want to mirror a VG called VG01 which has 1 9GB disk. If you want to mirror this, you need another disk of 9GB. Add that disk as a part of this VG and then mirror the LV's on the original disk to the new disk. You can do with a smaller capacity disk if the amount of data on the original disk is less, say if the data is 4GB, you can use a 4GB to mirror this data. However this is not advised. you should be using a 9GB disk to mirror a 9GB disk. this mirrored disk cannot be used to mirror data belonging to another VG.

So you see, if you have 10GB disk space free on external disk, you cannot mirror data from any VG to that, you can put the mirror on those disks for the lv's belonging to that VG only and not from other VG's.

Hope this helps.

Regds

Re: Disk Mirroring

Sanjay_6 — Tue, 12 Feb 2002 14:05:54 GMT

Hi Terry,

Take a look at these threads,

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-90672/B2355-90672_top.html&con=/hpux/onlinedocs/B2355-90672/00/00/69-con.html&toc=/hpux/onlinedocs/B2355-90672/00/00/69-toc.html&searchterms=mirror&queryid=20020212-061113

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-90672/B2355-90672_top.html&con=/hpux/onlinedocs/B2355-90672/00/00/70-con.html&toc=/hpux/onlinedocs/B2355-90672/00/00/70-toc.html&searchterms=mirror&queryid=20020212-061113

Hope this helps.

Regds

Re: Disk Mirroring

TMcB — Tue, 12 Feb 2002 14:13:22 GMT

Thanks everyone for all your help

Re: Disk Mirroring

Vincent Farrugia — Tue, 12 Feb 2002 14:27:16 GMT

Hello,

When mirroring, you need to specify another disk. It's a requisite of Mirror-Ux.

I don't know what the external enclosure you have is, but if you are going to mirror, I suggest that you mirror across controllers. That way, if one controller fails, you can still access the other disks through the non-failed controllers. If all disks are on the same controller, there is no point of having a mirror (except if the disk fails) cuz you still can't access the mirror if the conttroller fails in this case.

HTH,
Vince