[mythtv-users] Fastest RAID for HD?

[Emery Guevremont]

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.
>
>
>   
Well the fastest RAID is RAID0, except one bad hard drive and everything 
is lost. With RAID10 he'll loose too much disk space. With 5x500G disk, 
he'll have a 1TB raid partition with one spare I guess (depends how you 
use the 5th disk). With Raid 5, the more disk you have the better the 
performance and he'll have 2TB of space with some fault protection.

Protection, speed, space, pick any 2. RAID5 is the closest thing to all 3.
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