[mythtv-users] Why RAID 5 stops working in 2009

[John Finlay]

John Drescher wrote:
> On Fri, Oct 24, 2008 at 3:45 PM, Mache Creeger <mache at creeger.com> wrote:
>   
>> I have been watching the discussion that I kicked off with my post and I
>> still don't have a good feeling on what we are all supposed to do for 2009.
>>
>> I just installed a 4 x 1TB RAID5 array for a net of 3TBs. Given the URE
>> argument, the next step should be ZFS. However while a less than optimal,
>> user-space-based, fuse-based, ZFS is available, a kernel-based ZFS is not
>> currently available or planned because of licensing issues.
>>
>> So my questions are:
>>
>> Going forward, what are best mythtv practices for many large disk drives?
>>
>>     
>
> At work I have 75+ SATA / IDE drives in raid 5 and 6 arrays I and I
> have no fear at all about this URE stuff. Never had a single URE in 7
> years. At home I am moving away from raid for my storage. And the
> reason is power management. I mean with a raid array all of your disks
> will probably need to be spinning 24/7. With individual drives and
> storage groups I can power down drives after a few hours of
> inactivity. And I mean a few hours. I do not want my drives powering
> up and down all day causing them to die prematurely.
>
> BTW, right now I have 3 x 320 GB in raid 5 + 1 x 400 + 1 x 750 + 1 x
> 500. And 80 % of this is allocated to mythtv. I plan to split up the
> raid 5 array soon.
>   
My understanding is that raid5 and raid6 write performance is sensitive 
to the size of writes compared to the stripe size. Assuming that is true 
what would be the optimal stripe size for a mythtv raid5 for recording 
HDTV? Can the size of mythtv read and write sizes be adjusted to improve 
performance for a storage group on a raid5 array?

John

John