[mythtv-users] Software RAID5 faster than RAID10?

Raymond Wagner raymond at wagnerrp.com
Mon Apr 13 22:26:34 UTC 2009


Brian Wood wrote:
> On Monday 13 April 2009 14:02:49 Raymond Wagner wrote:
>   
>> Ben Curtis wrote:
>>     
>>> <snip>
>>>       
>
>   
>> Of course this is all moot for storing recordings.  One independent disk
>> for each tuner that could be recording simultaneously is the ideal setup.
>>     
>
> Of course that depends on what you mean by "ideal". As long as your storage 
> system can handle the maximum possible demand if all your tuners are 
> recording, there is really no need to go beyond that. You also have to 
> consider playing back multiple files, if your system allows that
What I meant by that is that sequential performance is irrelevant for 
all but lossless transcoding.  If you're recording 5 streams at once to 
a single device (physical or raid), most of your time is going to be 
spent seeking around the hard drive.  Your throughput will plummet, and 
a multi-disk RAID will not provide significantly better performance than 
a single disk.  During playback, (depending on your file system and 
tuning) those files will all be fragmented, and again you will have 
decreased performance.  You want to give myth as many independent 
spindles as you can.

Two 500GB RAID1 arrays would be better than one 1TB RAID10 array.  If 
you have the physical room, a couple of smaller old drives, and a 1.5TB 
RAID5 array would be better still.  Record to the assorted disks, and 
then either delete after watching, or transcode and move them over to 
the array.  Remember that all these drives can be spun down while not in 
use, so the additional power consumption is not significant.


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