Veritas root disk mirroring

Hi there,

My task is to replace the two 73 G disks with two 143 G disks , which has vxvm 4.1 running on it. I would like to know whether the steps iam following are correct.

1. Break the sub-disks, plexes of the root mirror.
2. Remove the sub-disks,plexes of the root mirror.
3. Remove one of the hard disk(eg. c0t1d0) and replace new.
4. Initialize the new disk and create subdisks and plexes
5. Attach the subdisks and plexes to the existing volumes
6. once there's no task in vxtask, do the same for the primary root disk(c0t0d0) also.

i would like to know whether i need to de-encapsulate the root disk before i do this.and also do i need to perform these in single-user mode? and also do i need to export the disk-group before i do these?

Please correct me if iam wrong.

Any help would be greatly appreciated.

The answer depends somewhat on the reason for replacing the disks, are you going to change the sizes of encapsulated filesystems or do you want to add new partitions or something else, you may or may not need to de-encasulate depending on your reply.

also as this is a rootdisk, when mirroring you MUST use vxrootmir to mirror the root filesystem or the second mirror will not boot.

Hi,

Thanks for your quick reply, actually due to size constraints i decided to replace 73G with 143G drive but i need the same data to be there in new disk and i dont need to increase the root file system, i want to create some new volumes in those new disks.

I was thinking about vxdiskadm, option to remove failed disk and replace.

Once i replace one disk at a time,it'll initialise it and can i mirror it using vxdiskadm itself?

Thanks

Ok, you have something of a messy situation to deal with here.

And just a couple of comments:
1. If you have any other diskgroups, condier using them instead.
2. If you only have 2 disk why use veritas? Encapsulated roots are a pain SVM is a whole lot simpler for boot disks.

I generally don't like to use vxdiskadm, so I'm not
sure what options you've got there.

The basics:

for each plex on the mirror:

vxplex -g bootdg -o rm dis <plex>

then

vxdg -g bootdg rmdisk <mirror_disk_name>
/etc/vx/bin/vxdiskunsetup <mirror_disk_media_name>

remove mirror disk, and replace.

devfsadm -Cv
vxdctl int
vxdctl enable

layout the new partitions on disk

/etc/vx/bin/vxdisksetup -i c0t1d0 format=sliced
vxdg -g bootdg adddisk rootmirror=c0t1d0 
/etc/vx/bin/vxrootmir rootmirror

for each other volume

vxassist -g bootdg mirror <volname>

repeat the procedure for rootdisk, no need to unencapsulate.

Hi,

Iam sorry for not quoting the details properly.

Actually I have 4 disks of which the other 2 disks belong to other diskgroup. I understand that SVM is more simpler and effecive for mirroring root disks but the company std. is like that.I cant do anything abt that.

Thanks for your step by step procedure. I'll try these steps.

Thanks.

It makes sense now, still that is a legacy thing, we have it here too. In the old days you had to have encapsuled disks if using veritas, now it's not required, but most companies continue to do so anyway, besides netbackup disn't play nice with SVM and a lot of folks have netbackup for backups.

I would not recommend this. Once the 2 internal boot disks are mirrored, you should consider a 'set it and forget it policy'. If you absolutely must have bigger boot disks (not sure why) you need to rebuild the system and restore/migrate data. Hopefully you have a spare server around to build the new disks on. If your just looking to add more disk space cause your requirements are growing, just create a new disk group and start adding the disks to the disk group.

best practice for veritas is to mirror internals and NEVER put anything application related on the internal disks. Sometimes this cannot be helped and small things end up on boot drives. But everything else should go on external.

Of course this is just my opinion. I would not risk a system that is purring like a kitten.

-S

I agree with this.

This is nonsense, you don't HAVE to do any such thing.

Excuse me? If you can find any Veritas document which states any such thing, can you please post a link? A general good practice is to keep the root disk mirrored and keep applications off it, there is no reason to tell someone they shouldn�t use internal disks for applications.

This is from my experience. I recommend not using internals for major apps. Sometimes small things can creep up and need to go on internal, small things can be dismissed.

There is no doc. This is my experience. Putting things on internal disks can cause many issues, just one of which is performance issues. You dont want to put a major database on there. Of course, you have to strike a balance. I was merely stating that major apps should not really go on internals. I wont budge from this stance.

You dont have to do anything. The previous thread states all the info you need. I clearly stated that this is my opinion. Not sure why you are antagonizing me.

-Sowser

I was correcting misinformation which you posted, as is required of moderators on this site. Nothing more and nothing less.