[OSX-Users] Re: More backup questions, was: Re: backing up while on road away from time capsule

[Steve Harris]

On 17 Sep 2011, at 14:23, Jules Field <sysjkf at ecs.soton.ac.uk> wrote:

> 
> 
> On 16/09/2011 19:14, Hugh Glaser wrote:
>> On 15 Sep 2011, at 11:45, Jules wrote:
>> 
>>> Lion will continue to do Time Machine backups to spare space on your laptop's own hard disk while it's away from its Time Capsule. Obviously this is no protection against disk failure, but it does provide protection against accidental file deletion or corruption.
>> Wow. I didn't see that. That is really cool - just what I want it to do.
>> 
>> New questions (there seems to be precious little about this on the net):
>> I think I'm going to Mirror RAID my TV programmes, etc. disk, as protection against device failure.
>> 1) Can I create a Mirror RAID Set using Concatenated Disk Sets as the components?
>> 2) If I add more than two Disks (or Concatenated Disk Sets) to the RAID Set, will it do the clever stuff to give me RAID 5, or whatever? I am guessing not - it will just do multiple mirrors?
> It won't do (2), you would only ever end up with more faces to the mirror. Converting a RAID 1 mirror into a RAID 5 requires a total reorganisation of the data, they are *very* different beasts. AFAIK nothing will automatically convert a RAID1 to RAID5 just because you add more disks, I've certainly never seen anyone's product attempt that trick. If it were to do it, you would lose all redundancy (and therefore safety) while it attempted to do it, and it will take a very long time to achieve.

It's possible drobo's do something similar, but they not truly RAID-anything (as far as I know), and I hear bad things about their reliability. 

- Steve