[mythtv-users] Fastest RAID for HD?

Markus Schulz msc at antzsystem.de
Thu Feb 14 15:10:32 UTC 2008

Am Donnerstag, 14. Februar 2008 schrieb John Drescher:
> On Thu, Feb 14, 2008 at 9:49 AM, Mark Hutchinson <mark at onnow.net> 
> > 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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