[mythtvnz] File System for RAID-5

[James Booth]

On Monday 15 June 2009 21:49:20 Hadley Rich wrote:
> On Mon, 2009-06-15 at 21:38 +1200, Jim Cheetham wrote:
> > If you lose a second drive while one drive is out of action ... you
> > lose data. Gone.
>
> Same as your two disk RAID1.
>
> > RAID5 doesn't give enough protection for your data, especially given
> > the relative costs of media today. It has horrible failure modes,
> > especially given that we don't know about drive health (most drive try
> > self-healing without telling the OS that it's happening ... only
> > informsingthe OS when a fatal error has occured). For big systems,
> > RAID5 does not deliver decent performance (unlikely to be important
> > for MythTV usages)
>
> Disks fail and notify how they do, no matter what arrangement they are
> in.
>
> RAID5 has enough performance for most things, is cheaper and is easy to
> grow.
>
> They both still have their uses.
>
> hads

I think Jim has a point. All my drives were reporting A-OK through SMART, and 
the failed drive still reports OK - it just throws I/O errors and locks up if 
you try to write to it. I have read a couple of research papers which have 
come to the conclusion that SMART is almost useless for predicting when a 
drive will actually fail, and (from memory) around half of drives fail without 
any prior warning.

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