[mythtv-users] Fastest RAID for HD?

Blammo blammo.doh at gmail.com
Sat Feb 16 05:07:58 UTC 2008


Without wading into all the fun things said in this thread, I had to
respond to a couple...

>  From what I have read, people seem to find RAID 5 too slow for writes.

Keep in mind, even with HD, we're talking about requested writes of up
to 20+megabit per second, or around 2 megabytes per second. As other
posters have pointed out, even a single drive can keep up with
multiple tuners worth of 2M pieces without dying. Raid5 multiple
drives is going to be no worse, overall, than a single drive for WRITE
performance.

However, for Myth usage, above the minimum, we don't care about WRITE
performance. We care about READ performance. Things like commerical
flagging, transcoding, fast-forwarding HD contect, multiple frontends
watching streams, all of those can tap the performance of a single
drive, especially when done in combination. Here's where the striping
benefits of raid5 (for example) on reads, will begin to show real
advantages.

> .... software raid is a lot better than hardware raid.

As other posters have responded, as a generalization, that's simply a
false statement. There's a reason that most, if not all, high-end
servers use hardware raid. Speed, reliability, performance, all are
improvements over software raid, and in some cases monsterous
improvements.



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