Re: block level vs. file level

[it <itech@kfa.org>]

>
>
>Yes, and it's a pain, but if you have to deal with it I think the
>wealth of options in md leaves you better able to handle it than
>with hardware RAID.  Here's something that happened to me:
>
>http://strugglers.net/wiki/becks.strugglers.net
>

Ouch.

How does hardware raid deal with this? Does it?

Thanks,
A.


Andy Smith wrote:

>On Sun, Feb 12, 2006 at 11:31:07AM -0800, it wrote:
>  
>
>>The hardware raid does the mirroring on the block level, so it's 
>>actually /dev/sda mirroring /dev/sdb - the whole drive, and not 
>>partitions. There is a way to set this up on software raid. It takes 
>>more configuration tweaking, but the mirroring then includes the 
>>partition table as well. This way, if a drive fails, one can replace it 
>>without pre-partitioning it.
>>    
>>
>
>That can be less flexible though.  If I have say 4 drives then I
>quite often want small /boot, / and swap under RAID-1 then the rest
>as a single large partition in RAID-5, -6 or -10 as an LVM PV.
>
>  
>
>>This also raises another point, which is relevant for both cases - same 
>>exact models of hard disks have different number of cylinders, so if a 
>>RAID partition is created on a larger drive it cannot be mirrored to a 
>>smaller drive.
>>    
>>
>
>Same exact models don't usually have different block counts, but
>certainly if you replace a dead drive with a different one of the
>same advertised capacity you can end up getting one slightly
>smaller.
>
>  
>
>>Does anyone have any experience with this?
>>    
>>
>
>Yes, and it's a pain, but if you have to deal with it I think the
>wealth of options in md leaves you better able to handle it than
>with hardware RAID.  Here's something that happened to me:
>
>http://strugglers.net/wiki/becks.strugglers.net
>
>  
>