Re: OT: harddrive addition for RAID

[Camaleón <noelamac@gmail.com>]

On Mon, 17 Oct 2011 23:47:45 +0100, Richard wrote:

> On Mon, 17 Oct 2011 17:12:00 +0000 (UTC) Camaleón <noelamac@gmail.com>
> wrote:

>> > 2 questions:-
>> > 
>> > 1. does the HD need to be exactly the same as the one its being
>> > paired with ?
>> 
>> Not necessarily, but you will lose the remainder difference space
>> between the smallest and the bigger of the disks. If you were referring
>> to the brand/model/serial number of the disks some people think is
>> better they exactly match (me) others think the opposite.
>>  
>> > 2. how easy is it to change from a non RAID config to a RAID config.
>> > ie.
>> >  can I just  put in the second HD and run something to automagically
>> >     change the config to RAID ?
>> 
>> I don't think so... manual reconfiguration is required which usually
>> involves more than one command.
>> 
>> 
>> 
> Thanks Camaleon
> The reason I ask about matching the HDs is that I have a Hitachi 500 GB
> drive, I can add another 500 GB HD for GBP 32, but if it requires an
> exact match a Hitachi 500 GB HD will cost around GBP 50.

There is no need to match the "exact" serial number, but the hard drive 
technical specifications (seek speed, cache size, interface...) to avoid 
having the array always degraded because of i.e., timeouts.

But you can perfectly buy a Segate, WD or Hitachi hdd (now part of WD's 
business) that pairs with the specs of your current hard disk. As I said, 
other users prefer doing it by this way to avoid having both disks with a 
factory error (in the event there has been an error on the manufacturing 
process, both disks will be affected, so choosing different brands 
reduces this possibility).

> As for question 2 , I had a feeling that it would have to be a manual
> process :(,
> 
> Comments appreciated

Ugh, nope. Dealing with software raid is a very consuming and difficult 
task, remember that you are "playing" with data, the most valuable 
treasure you have :-)

You have to care, for instance, about the bootloader and when something 
goes wrong, you need to make the proper steps to be able to boot the 
system with the raid in a degraded state.

Greetings,

-- 
Camaleón