[mythtv-users] .23/.24 NFS mounting / Storage Groups

[Raymond Wagner]

On 10/20/2010 19:36, Brian Wood wrote:
> On Wednesday, October 20, 2010 05:23:41 pm Scott wrote:
>> On Oct 20, 2010, at 5:22 PM, Brent Bolin wrote:
>>> My current setup is a back end with raid disk storage and tuners.  I
>>> also have a back end running in a Xen environment as a guest helping
>>> with commercial flagging.
>>>
>>> I also just upgraded my network to GB today.
>>>
>>> Flagging from the mythtv guest helps take the cpu load off the primary
>>> back end, but still puts a stress on disk I/O.
>>>
>>> I've been toying with the idea of creating another storage directory
>>> for mythtv recordings and that being an NFS mount from the primary
>>> back end.  One of my main concerns is creating a complected
>>> configuration.
>>>
>>> Is this the only way to spread disk usage between systems(NFS)?
>> Are the disks really stressed during commflag? I have a single disk SATA
>> 7200 RPM drive that records 3 HD streams from a HDHR while doing commflag
>> at the same time. Disk IO has never been a bottleneck on the system.
>>
>> If you do want to spread the work, your best bet for simplicity is more
>> physical drives in the same system. You can use mdtools or LVM to strip
>> data across two disks. to spread the work.
> Linear RAID or RAID 0 will "spread the load" and increase apparent disk performance, but also increase the probability of losing the array's contents due to a disk failure, as those systems provide no redundancy.

RAID0 is actually a detriment to recording performance.  If given 
independent drives, MythTV will default to balancing the load evenly 
across multiple drives.  Each drive will only have to seek between the 
recordings it is directly handling.  When doing RAID0,  every disk will 
be dealing with every recording, seeking back and forth between each, 
and your total throughput diminishes accordingly.