Creating omcdg disk group using VxVM

[Rajesh Karelia]

Hi,

This thread is in continuation with my previous thread in the forum but this gives very finer details which I would like to know/learn from all VxVM gurus. I am using VxVM 4.1 which does not require rootdg.


My requirement is as follows:
Create 'omcdg' with c4t1d0 and c4t2d0 with respective mirror set on c5t1d0 and c5t2d0.

'omcdg' disk group
=> with physical disks - c4t1d0(dsk_dbf)& c4t2d0(dsk_bck)
=> with repectively mirror sets as c5t1d0(dsk_dbf_m) & c5t2d0(dsk_bck_m)

There are 4 sub-disks.
dsk_dbf-01 (under dsk_dbf)
dsk dbf-02 (under dsk_dbf)
dsk_bck-01 (under dsk_bck)
dsk_bck-02 (under dsk_bck)

There are 4 plexes. (cud be more, I dont know)
srs_1_p0 (in dsk_dbf-01)
srs_2_p0 (in dsk_dbf-02)
srs_3_p0 (in dsk_bck-01)
srs_4_p0 (in dsk_bck-02)

There are 4 volumes.
srs_1_v (for srs_1_p0)
srs_2_v (for srs_2_p0)
srs_3_v (for srs_3_p0)
srs_4_v (for srs_4_p0)

There are 4 mount points.
/data/srs_1 (for srs_1_v)
/data/srs_2 (for srs_2_v)
/data/srs_3 (for srs_3_v)
/data/srs_4 (for srs_4_v)

I would like to create mirror set of c4t1d0 and c4t2d0 on c5t1d0 and c5t2d0 respectively. I am really confused how to go about it.

Should I create 4 more plexes as mirrors of the ones listed above and associate them to a particular volume (eg srs_1_v)?
OR
Is there any other way of creating mirror sets across disks?

Your help will be very much appreciated.

Thanks,
Rajesh

[Zinky · Accepted solution]

Create the omcdg diskgroup:

vxdg init omcdg dsk_dbf=c4t1d0
vxdg -g omdg adddisk dsk_bck=c4t2d0
vxdg -g omdg adddisk dsk_dbf_m=c5t1d0
vxdg -g omdg adddisk dsk_bck_m=c5t2d0

Create your mirrored volumes:

vxassist -g omcdg make srs_1_v nnnnn layout=mirror alloc=dsk_dbf,dsk_dbf_m

vxassist -g omcdg make srs_2_v nnnnn layout=mirror alloc=dsk_dbf,dsk_dbf_m

vxassist -g omcdg make srs_3_v nnnnn layout=mirror alloc=dsk_bck,dsk_bck_m

vxassist -g omcdg make srs_4_v nnnnn layout=mirror alloc=dsk_bck,dsk_bck_m


Where nnnn will be the number of blocks (1KB) each volume will have.

The above vxassist commands will result in:

v srs_1_v
pl srs_1_v-01
sd dsk_dbf-01
pl srs_1_v-02
sd dsk_dbf_m-01

v srs_2_v
pl srs_2_v-01
sd dsk_dbf-02
pl srs_2_v-02
sd dsk_dbf_m-02


... ditto for srs_3_v and srs_4_v.

Just rename the Plex names with the names you want...


Hope this helps and illustrative enough...

[Rajesh Karelia]

Thanks Nelson. That was really useful.

Continuing the same, how can I rename plex names which are created by vxassist commands?

I just came across another kind of mirroring using plex. Create 8 plexes, 2 on each disk. Take 1 plex from dsk_dbf and 1 from dsk_dbf_m and associate them to the same volume. This makes use of vxmake command of VxVM.

What is the difference between these 2 types of mirroring? Which one is better and suits my requirement of mirroring data across disks?

Thanks

[Rajesh Karelia]

Hi,

If someone can clear to my confusion/query in the previous reply, it would be really great for me.

Thanks,
Rajesh

[Zinky]

How to rename plexes (and any other VxVM objects)? Simple:

vxedit -g dgname rename oldname newname


There are 2 BASIC types of mirroring in VxVM,

(1) simple mirroring accross 2 disks - what I've just illustrated

(2) striped mirrors:

vxassist -g omcdg make xxxvol NNNN layout=stripe,mirror ncols=N {stwidth=N}

or

vxassist -g omcdg make xxxvol NNNN layout=mirror,stripe ncols=N {stwidth=N}


Read the vxassist man pages specially the "Layout" section.



Havcing more than 1 subdisk from the same disk as a member of your stripe does not make sense.

[Rajesh Karelia]

Thanks Nelson, that was useful.

Cheers
Rajesh