Disk selection recording algorithm

[gcrafton]

I'm new to SageTv so this may have already been discussed before.

I have 2 recording drives (formatted for 64K clusters) and was recording 3 HD channels last night starting at 8:00 and 9:00 while watch one of the channels. I was having some intermittent stutter, which I hadn't seen before.

When trying to figure out what the problem was I noticed that all 3 tuners were recording on one disk at 8:00 and then they all switched to the other disk at 9:00. So SageTV was recording 3 HD streams and reading 1 HD stream from single drive while the other was Idle. This is pretty I/O intensive for a single disk.

In looking at the documentation for SageTV it states that it will use the disk with the most free space to start the next recording (which is what it did). If I had 10 tuners and 10 disks with 10 shows recording all starting at the same time, SageTV would be writing 10 streams to 1 disk while the other 9 are Idle. It seems that this algorithm should be changed to better share the disk I/O load over the available disks.

Two possible solutions are:

1) As each tuner starts, it calculates how much space it will use and removes that from the free space on the disk that it is using. This would help spread the load once the disk have about the same free space, but would still have problems when adding a new large disk to your system unless you moved some files around manually to balance the disks free space.

2) Add a couple of properties to each disk to denote the number of recording streams it can handle, Standard and Max. Still use the free space rule to determine which disk gets picked to record on, but also check to see if the Standard number of recording streams has been reached to move to the next most free disk. After all of the disks are at their Standard number of recordings streams, switch disks for each new recording until the Max is reached.

I really love all the neat features that SageTV has, but the ability to function as a PVR without stuttering should be a priority.

[Opus4]

You could try playing with this property:
mmc/encoders/<some#>/forced_video_storage_path_prefix=

A couple links to previous discussions of its use are here and here.

- Andy

[White94Cobra]

I agree that Sage could use some work on what drive(s) it uses when recording multiple streams at the same time. As quasi work-around for this, I stagger the start time of shows that I know are on at the same time. On some nights I have 5 shows start at the same time. If I don't stagger their start time, sometimes 1 or 2 of the shows fails to start recording (I guess too much activity on one drive at one time). Assuming Sage is keeping free space on each drive balanced, this usually (but not always) allows for Sage to use more than one drive for simultaneous recordings.