[mythtv-users] Wiki: Balanced Disk I/O

[Douglas Peale]

On 08/11/2015 08:48 AM, Peter Bennett (cats22) wrote:
> Hi MythTV experts
>
> I am updating the wiki and wondering about the Balanced Disk I/O setting.
>
> https://www.mythtv.org/wiki/Storage_Groups#Balanced_Disk_I.2FO
>
> The above page recommends if you are doing more than 2 recordings at once to use this setting to get recordings put on
> separate file systems to avoid buffer overruns. I am thinking of changing that recommendation.
>
> A quick back of the envelope calculation tells me that I could record some 50 HD programs at the same time on one disk drive,
> based on 1 Gb/sec transfer rate and 8 GB per hour on each HD recording.
>
> Clearly 50 at a time is theoretical and unlikely because it would be affected by seek times. However HD programs vary from 3
> GB to 8 GB per hour which means even more than 50 at the same time.  Also drives are rated at 6 Gb/sec which means 300 HD
> recordings at the same time(!).
>
> You could surely record at least 10 HD programs at the same time or maybe many more, so unless you have a very unusual
> situation it seems that you need not concern yourself about hard disk performance.
>
> I have 6 tuners and have never had a disk performance problem, even while watching at the same time as recording, but I have
> probably not recorded 6 channels at once.
>
> Does anybody have an opinion on this?
>
> Peter
>
>
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When I had a single disk system, I very often had glitched recordings. I believe it was the database using all of the disk
bandwidth starved the recording stream of bandwidth until its buffers overflowed.
I have not had trouble since I put the recordings on rotating media, and the data base on a solid state drive.
I have 5 HDHomeRun tuners and an ATI HDWonder tuner in my system, but I was having problems even though the system seldom
recorded more that two shows at a time.
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