Mirroring

[rang vivien]

I want to know what's the difference between software
mirroring and hardware mirroring. How can I check which
kind of mirroring is being used in my system?
Thanks ahead!

[Paul Heffels_1]

Hi,

In software mirroring there is a driver that writes data to both copies. So
each block of data needs to be written twice. This uses extra processor time.

A hardware mirror uses a separate controller that handles all the write
requests. The OS gives the write command only once and the controller actually
writes the data to both copies. This is much faster (although there can be
situations where it isn't, ask me about it if you're interested).

You can check whether a logical volume is mirrored by isuing the following
command:
lvdisplay /dev/vg00/lvol?

Look for "Mirror copies". Behind it are the number of copies for that logical
volume.

To check for hardware partitions you need to access the configuration for the
hardware device. How to do that depends on the solution you use. Check for
manuals.

[Mabo David]

On HP-UX, you are probably using software mirroring if you use Mirror-UX. If
you have a raid system, then you are probably using hardware mirroring.

If you have a Jamaica HA subsystem, then it is not a raid, but if you mirror,
it is software.