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

[Thomas Fjellstrom]

On Friday 24 October 2008, Steve Heistand wrote:
> Thomas Fjellstrom <tfjellstrom at shaw.ca>, said on Fri Oct 24, 2008 [05:58:46
> PM]: } On Friday 24 October 2008, Steve Heistand wrote:
> } > } >
> } > } My understanding is that raid5 and raid6 write performance is
> sensitive } > } to the size of writes compared to the stripe size. Assuming
> that is true } > } what would be the optimal stripe size for a mythtv raid5
> for recording } > } HDTV? Can the size of mythtv read and write sizes be
> adjusted to improve } > } performance for a storage group on a raid5 array?
> } >
> } > true, but this falls under the hurry up and wait category.
> } > even the worst performaning raid is faster then hdtv needs.
> } > bad raids give 20M/sec, uber HD signal needs about 5M/s.
> }
> } Wow, 20M? My laptop's single pata 5400rpm disk gives me 40 :o I get
> 200-300 } from my new raid5 (4x640 sataII).
> }
>
> its not doing the md5 sums while its writting on a really slow cpu now is
> it :)

Um, no, but I did have had my old array (2x320) in degraded mode for months at 
one point. Even then it was reasonable. And it was running on a rather 
overloaded 2.4Ghz Athlon XP (was running vms and such).

> that is the really low end at 20M/s, good consumer hardware raids can
> do ~500M/s we have some enterprise raid systems at work that can squeeze
> 2-3G/s without any trouble.

Youch. I'd love to see that.

-- 
Thomas Fjellstrom
tfjellstrom at shaw.ca