[mythtv-users] Fastest RAID for HD?

Mark Hutchinson mark at onnow.net
Thu Feb 14 15:15:49 UTC 2008

On 14-Feb-08, at 8:10 AM, Markus Schulz wrote:

> Am Donnerstag, 14. Februar 2008 schrieb John Drescher:
>> On Thu, Feb 14, 2008 at 9:49 AM, Mark Hutchinson <mark at onnow.net>
> wrote:
>>> I have read a bunch of docs, but wanted to get some feedback or
>>> reports of results.
>>> HD system.  firewire capture etc....  3ghz Core2Duo, 5 sata ports.
>>> I have 5-500gig sata drives for storage.
>>> LVM would work, but provide no RAID.  RAID 5 is too slow from what
>>> I have read.
>> With a modern CPU write speeds are > single disk speed but things
>> slow down when you have a lot of thrashing. Read speeds are  nearly
>> RAID 0 for N-1 disks. I get 266MB/s hdparm reads on a 6 drive
>> software raid 6 (AM2 Althlon 3000 single core + 2GB PC6400 DDR2 + 6 X
>> 320 Segate 7200.10) and 90MB/s writes.
> raid5/6 has the problem that for each write he must read from all  
> other
> disk to generate the new hash values.
> Best write performance with redundancy you will get by RAID10.
> At work i've build a pgsql-maschine with 6 73GB SAS 15k disks RAID10  
> and
> got 320MB/s read _and_ write. A RAID5/6 don't get much more write  
> speed
> then the write speed of a single disk.
> But i think for a mythtv storage write performance from raid5/6 will  
> be
> enough and the better solution compared to diskspace-loss from raid10.
> -- 
> Markus Schulz
> Programming today is a race between software engineers striving to  
> build
> bigger and better idiot-proof programs, and the Universe trying to
> produce bigger and better idiots. So far, the Universe is winning. -
> Rich Cook
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 From what I have read, people seem to find RAID 5 too slow for writes.

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