Re: Use mixed sizes drives in the same Raid string

It may not matter to your client, but if they are contemplating moving to a
Power7 system in the not-too-distant future, the Power7 550 does not support
drives smaller than 70GB (internally or in a rack/side car). I don't see
any reason to believe the 720, or whatever the 520's replacement will be
called, will be different.

On Thu, Apr 15, 2010 at 8:51 AM, Marco Facchinetti <
marco.facchinetti@xxxxxxxxx> wrote:

Inline2010/4/15 <rob@xxxxxxxxx>

It's not just the saving of a few euros. It's also
- Reduction in power consumption. That side car is going to suck energy
and require additional power feed(s).

This is a point that supposed to be important (at least to my consience)
but
the customer main business is selling energy so I don't think they are so
sensitive about this matter

- Increase in speed. The 70GB drives are 15K speed versus 10K speed. If
you're bad at math that's a 50% increase in speed. Extremely

significant!

This speed will outweigh the additional disk arms you will be getting.
Been there, done that.

If I'm not wrong 4326 are 15k, see:


http://www-03.ibm.com/systems/resources/systems_power_hardware_reports_io_specs.pdf

- Affect on cooling. You add a sidecar, you add BTU's.

See the first point...

You are running an i. Therefore you can have faith in your backups
(providing you follow the steps). Hundreds of us have done
unloads/reloads.

This is the sad part: most of the 520 of my customers mount tape 6384
(30/60
gb) so there are two negative point:

- This unit is not reliable as used to be in other formats (I have some
customers with a very high rate of device failure)
- The system save requieres 3 tapes so the customer has to pay samebody for
it.

At the end the balance is so "balanced" that (I think) the customer will
choose the expansion unit.

Let's see

Thanks again

MarcoF

Rob Berendt
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