Re: Sharing disks amoung multiple software RAIDs

[Helge Hafting <helge.hafting@aitel.hist.no>]

Kasper Sandberg wrote:
> On Fri, 2008-05-02 at 00:06 -0700, David Rees wrote:
>   
>> On Thu, May 1, 2008 at 7:42 PM, Kasper Sandberg <lkml@metanurb.dk> wrote:
>>     
>>>  in other words, would i be
>>>  safer to run rsync every day to my other disk, and run in non-raid
>>>  mode?!
>>>       
>> What would be safer is to run rsync every day from one redundant array
>> to another array - preferably on another machine that is located as
>> far away as possible from the one that you are backing up.
>>
>> RAID is not the same as a backup, though unfortunately, too many
>> people treat it as such.
>>     
> Im not treating it as a backup, what i want, is to make sure that if 1
> disk dies, the data is still intact and ill hopefully be able to run
> with 1 disk till the newly ordered one arrives - and while i naturally
> will keep offsite backups of most important data, it is certainly far
> easier to simply rip out a faulty disk, and put in another, instead of
> restoring from backup from scratch..
>
> So my question remains.. Is md raid1 not suited for this need? would it
> be safer to run in non-raid1 mode and daily(maybe hourly) rsync
> everything over to the second disk?
>   
Raid protects against disk failure. So your use  is fine.

Backup also protects against user error and virus/worm/cracker damage.
If you accidentally overwrite a file, or a virus/worm/cracker messes up 
the filesystem,
then RAID loose because the overwiting/messing happens on both disks.
In that case you'll still be able to get stuff from a backup.


Helge Hafting