I'm not sure if this is a kernel-ide-disk issue or a raid issue, so I'm trying here first: I've built a frankenstein file and mythtv server with RAID 6 8x250GB + 2x300GB disks for 2TB usable space. I used 4 generic PCI (Promise, 2xSyba(SiI_IDE), C-Media) and onboard(Intel)+onboard(Promise) PATA controllers. (The 2 bigger 300 disks also house my root/boot/swap RAID1 partitions.) I know, cheesy, but this is a SUPER cheap way to get GOBS of storage space... those IDE cards are cheap and most of my money goes to drives. Works great... except for during heavy disk access my MythTV recordings will get somewhat glitchy audio. Stop the disk access and the audio returns to normal. Even with moderate disk access it's ok. It's just when it's heavy. And the glitches are usually every few seconds unless it's really heavy where the audio gets nearly unintelligible for 10 secs or so. The audio, and the video, come through USB2 from a Plextor hardware MPEG4 encoder. The video +audio stream is not disk intensive, only about 600k/sec. However, the way the Plextor works is the audio is software-encoded into MP3 on the fly (ie: not in the Plextor like the video). My video almost never glitches -- it's just the audio. If I run some simple tests I can make it glitch recording some TV while doing something like copying a duplicating a large TV file with cp. The CPU load never gets above 34% and bounces between 25-35%. I have done all the hdparm tweaks I can think of including: DMA (-d1), unmasqirq (-u1), lookahead, multiple io 16, 32bit transfers. I tried using an SMP kernel (it's a UP system) for enhanced APIC. All drives are running as master with NO slaves except for 1 (unused during the tests) optical drive. I did used to have 2 drives as slaves and no unmasqirq and it was really bad, and things did improve when I moved to all-master and enabled unmasqirq. It's like if I could tweak it just a little more I'd have it perfect. The CPU is a not-slow Pentium 4 2.4/400 on Intel 845D chipset. RAM is 1GB ECC. Anything else I can try tuning to fix this nagging issue? Any ideas on what's biting me here? Thanks! And Merry Christmas to all! - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
