[mythtv-users] Why RAID 5 stops working in 2009

[Thomas Fjellstrom]

On Friday 24 October 2008, John Finlay wrote:
> David Brodbeck wrote:
> > On Fri, October 24, 2008 1:57 pm, jedi wrote:
> >> On Fri, Oct 24, 2008 at 01:54:11PM -0700, David Brodbeck wrote:
> >>> On Fri, October 24, 2008 12:45 pm, Mache Creeger wrote:
> >>>> Should we just pray that although the statistics say otherwise,
> >>>> native RAID5 on Linux will not self-destruct when using many large
> >>>> capacity drives?
> >>>>
> >>>> Any ideas?
> >>>
> >>> Don't use RAID 5.  Use RAID 10 instead.  See this page for a humorous
> >>> take
> >>> on why:
> >>> http://www.miracleas.com/BAARF/BAARF2.html
> >>
> >>     ...I've been thinking not RAID 10 but LVM on top of RAID1.
> >
> > Sure, that's basically the same thing.  RAID 10 just means you're taking
> > a bunch of RAID 1 mirrored pairs and striping data across them RAID 0
> > style. RAID 01 is the opposite; it's taking two identically-sized RAID 0
> > stripes and mirroring them.  Functionally the two are equivalent, except
> > I think RAID 10 has some advantages when you have to rebuild.
>
> I think raid10 has better failure characteristics i.e. if a disk on
> raid01 fails it knocks out the whole raid0 its in so only half the disks
> are still working while with raid10 if a disk fails then only one disk
> is knocked out and the other disks are still working.

And if you use the new linux raid10 module instead of using separate arrays 
for each layer, you get the benefit of one single array, and it can manage 
uneven numbers of disks.

The only reason I went with raid5 again is because I really didn't want to 
loose 640G more of space to redundancy. I just hope it doesn't bite me in the 
butt later.

> John
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-- 
Thomas Fjellstrom
tfjellstrom at shaw.ca