Chris wrote: >hello List, > >I have one PVR500 and a PVR150. so 3 tuners in total. > >they record to an LVM volume (2 partions on 2 sata disks) > >when i record with all three tuners at the same time I have one >recording that drops a lot of frames. > >I read somewhere that it's not good to share 1 irq for 2 ivtv cards. > >Well that is what happens.. > >cat /proc/interrupts |grep ivtv > 19: 186698 IO-APIC-level ivtv0, ivtv2 > 20: 1586430 IO-APIC-level ivtv1, nvidia > >Could this be the source of my problem ? Or should I just invest in some >lightning fast sata disks in a raid whatever (depends on my financial >posibilities :-) ) > >
I would bet your disks are plenty fast and you have some sort of software / driver issue, but perhaps the below will help you figure it out. Keep in mind that your recordings are at most a few megabytes per second and a single disk should be able to do at least 20-30 MB/sec. Are your two lvm disks configured as a stripe (raid0) or just a plain concatenation? Stripes are obviously faster as blocks read/written are more balanced across the physical devices. See lvcreate(8), -i option. For optimal performance, the disks should be on separate IDE cables (but you say they're SATA, so this doesn't apply to you, but maybe someone will find this tip useful). While 99% of the time it's not the problem, double-check that DMA is enabled on the disks using 'hdparm' (forgive me if that doesn't apply to SATA; I have yet to use one). What does 'iostat -x 1' display for %util[ization] while recording? Do you have any significant bursts where it's 100% for several seconds? (100% bursts for one second or so every 5 seconds can be 'normal' as the kernel flushes unwritten file data). If you do, your disks are a likely bottleneck. Are there any syslog messages or mythbackendlog messages? If you carefully correlate the time you see dropped frames in your recording (look at the current position with "i") to the times in the syslog, you might be able to find the appropriate area in the logs to look for abnormal messages. Regards, Chris _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
