Very Computer

by **Lee Yam Fo** » Sun, 31 Dec 1899 09:00:00

hi,

our company provides backup service for a client runnig Informix-online v6(?)
on RS/6000 950 with AIX v3.2. we have little knowledge on AIX and none on
Informix. here is the question:

with every physical disk, the client create a volume group and then partition
the volume group into logical volumes of certain sizes. some of these logical
volumes will be used as raw disks for storing informix database.

because the disks size of our machine are different from their disks and
our total disk space is less than theirs, to save space, we want to group
all our disks into a large volume group and then partition it into logical
volumes efficently. for each informix volume , we will create a logical
vulume with exactly the same size and name as that on the client machine.
When restoring database from informix-format backup tapes, will there be
any problem? we were told by the client that informix bypass AIX's logical
volume manager and access the disk directly . Therefore, the approach will
not work once the disk gemotry is changed.

I don't believe informix is that stupid and inflexible. if this is true,
we will be in big trouble. please advise me on this.

Thanks

Joe Lee

by **Mark Neum** » Sun, 31 Dec 1899 09:00:00

Quote:>hi,
>our company provides backup service for a client runnig Informix-online v6(?)
>on RS/6000 950 with AIX v3.2. we have little knowledge on AIX and none on
>Informix. here is the question:
>with every physical disk, the client create a volume group and then partition
>the volume group into logical volumes of certain sizes. some of these logical
>volumes will be used as raw disks for storing informix database.
>because the disks size of our machine are different from their disks and
>our total disk space is less than theirs, to save space, we want to group
>all our disks into a large volume group and then partition it into logical
>volumes efficently. for each informix volume , we will create a logical
>vulume with exactly the same size and name as that on the client machine.
>When restoring database from informix-format backup tapes, will there be
>any problem? we were told by the client that informix bypass AIX's logical
>volume manager and access the disk directly . Therefore, the approach will
>not work once the disk gemotry is changed.
>I don't believe informix is that stupid and inflexible. if this is true,
>we will be in big trouble. please advise me on this.
>Thanks
>Joe Lee

This is not the case. Informix will use the device
/dev/logical_volume_name to access the data and it will be relitive to
the logical volume and AIX will handle the physical disk mapping.
That is why you need to chmod the /dev/LV to informix.informix so
informix will "own" that logical disk. An important thing to mention
about informix backups is that although Informix does not care what
the volume group name is it does very much care about the "name" of
the logical volume that the databases are built on, and there can be
more that one. Therefore, I suggest that you do as I have done and
create logicaly named links to the logical volumes for Informix to use
rather than directly naming the logical volume names. This will
provide you flexability in recreating logical volumes, then create the
links, and procede with the restore operation. I have been caught in
the past where the customer had already created a logical volume with
the same name that I wanted to use and was unable to restore the data,
by using links you can avoid this problem.

Mark Neuman
Datatrend Technologies,
(612) 938-7608

Very Computer

Informix on AIX using logical volume

Informix on AIX using logical volume

Informix on AIX using logical volume