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Re: raid 5/6 with different controller



In article <9QCxc-7zz-7@gated-at.bofh.it>,
 "Douglas A. Tutty" <dtutty@porchlight.ca> wrote:

> On Mon, Jan 28, 2008 at 11:33:12AM +0100, Pol Hallen wrote:
> > I need some information about the raid 5 (or 6) using 2 different 
> > controller 
> > (one integrated in the mother board: 6 sata disks, and other pci controller 
> > with 4 disks support).


> > 
> > Is there any problem about data security and/or performance?
> > 
> > Is it a bad idea? 

I have done this many times it works well.
Assuming linux software raid you need to match your stripe size to the 
ext2 stride size.
Also there are performance issue using ext3 the journal slows things 
down considerably.

For office type use I prefer to use EXT3. But for systems that are using 
the RAID as a huge transfer buffer I prefer EXT2 so as to avoid the 
journal.

for the best of both worlds (in theory) you can keep a partition on your 
system disk, or on a separate disk for the journal. In theory this would 
remove the performance constraint. You need to make sure you have a big 
enough partition for the journal. I have not tried this solution but in 
theory it should work.

> 
> Most motherboard's supposed RAID is BIOS-assisted Microsoft software
> RAID and doesn't work with Linux.  Which leaves Linux software raid.
> 
> Doug.


The other HUGE problem with cheap hardware raid is that in 5 years time 
when your controller dies there is no practical way to recover the data.
With software raid you will always be able to recover given any single 
HW failure.

Stuart.


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