[Veritas-vx] Volume type different

[Doug Hughes]

On Thu, 13 Feb 2003, nawir wrote:

> Hi expert,
>
> I want to know what is the difference between volume #1 (see below) and volume #2 in terms of volume type and advantage/disadvantage
> Volume #1 is created by me that I know exactly I am using concatenate pro while the other one is not by me.
>
> thanks
>
> 1. Volume with ConcatePro
> v  hroracle     -            ENABLED  ACTIVE   10485760 SELECT    -        fsgen
> pl hroracle-03  hroracle     ENABLED  ACTIVE   10485760 CONCAT    -        RW
> sv hroracle-S01 hroracle-03  hroracle-L01 1    10485760 0         4/4      ENA
>
> v  hroracle-L01 -            ENABLED  ACTIVE   10485760 SELECT    -        fsgen
> pl hroracle-P01 hroracle-L01 ENABLED  ACTIVE   10485760 CONCAT    -        RW
> sd hrorada02-02 hroracle-P01 hrorada02 0       10485760 0         c1t3d1   ENA
> pl hroracle-P02 hroracle-L01 ENABLED  ACTIVE   10485760 CONCAT    -        RW
> sd hrorada04-02 hroracle-P02 hrorada04 0       10485760 0         c1t3d3   ENA
>
> 2. Volume not created by me
> v  oracle       -            ENABLED  ACTIVE   8388608  SELECT    -        fsgen
> pl oracle-01    oracle       ENABLED  ACTIVE   8388608  CONCAT    -        RW
> sd disk02-04    oracle-01    disk02   46137344 8388608  0         c3t2d1   ENA
> pl oracle-02    oracle       ENABLED  ACTIVE   8388608  CONCAT    -        RW
> sd disk04-03    oracle-02    disk04   20971520 8388608  0         c3t2d3   ENA
>

In general:
a concat-pro volume is 1+0. it is more resilient in the face of failure.
You can lose 1 disk from each mirrored pair and keep running.
volume 2 is 0+1, you can lose one or more disks from one side (plex)

In this specific case there is no advantage to 1 because there
are only 2 disks. In fact, there is a slight disadvantage because
growing it is a bit more difficult to do in an understandable fashion.
For simple mirrors, use 0+1. Then you can grow it (and convert
to a 1+0 later) easier, in an understandable and easily viewable
way.