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| IO throughput on VIA EPIA MII12000 http://forum.linhes.org/viewtopic.php?f=2&t=5784 |
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| Author: | tuatara [ Tue Aug 23, 2005 4:25 am ] |
| Post subject: | IO throughput on VIA EPIA MII12000 |
Hi there, **** some background first - question below****** I have a knoppmyth 5.15 running well on an EPIA MII12000. Its got an internal disk (160GB Samsung) for OS, music, live buffers etc. Its also got an external firewire 400GB disk for TV/Video - the georgeous case only supports 1 internal HDD. Front and back on the one box. [Side note: on V5.15, USB2 HDD did not work. There was a problem in the linux kernel, documented on kernel dev sites. Fortunately firewire did]. I record all TV at max bitrate - about 2G/hour. Myth works well and is stable. I also run a couple of squeezeboxen and the squeezebox server on the mythbox (these are awesome devices - thoroughly recommended). I have noticed that when the backend is encoding, music on the squeezeboxes skips for some of the higher bandwidth music (most of mine is 320k LAME). Since music and recorded TV go to different disks, this skipping should not be be caused by throughput on the individual disks (I have DMA enabled, and hdparm reports 43MB/s on the internal drive, and 24MB/s on the external). So I am wondering if its an artifact of either firewire or internal IO in the EPIA. I dont believe its CPU bound - the squeezebox server is light, and encoding takes 2% CPU (PVR-350). ****** The questions ****** Question 1: I'd like to stop the music skipping when the backend is recording. Any ideas? Question 2: S.O. wants a second encoder card installed (two of her favourite programs at the same time). But I am concerned that if I am hitting some limit in the IO channels of the EPIA box, a second encoder card will simply cause dropouts or other problems. Has anyone done this with an EPIA? The external HDD reports 24MB/s - is that sufficient from a practical point of view? Question 3: Is this a problem with running disks over firewire? What is the practical throughput of multiple disks on firewire. Perhaps I should stripe multiple disks (RAID-1) for improved performance. Many thanks for any ideas you can share. Cheers. Paul |
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| Author: | Xsecrets [ Tue Aug 23, 2005 8:18 am ] |
| Post subject: | |
I have no idea about running disks over firewire, however 24MB/s should be enough bandwidth. If it were an internal drive I would ask if dma was enabled on it properly, however I have no Idea how that work or if it works with firewire. And a small correction RAID 1 is a mirror not a stripe set and does not help with performance. You are looking for RAID 0. However I doubt it will help in this instance. I would do some research on dma and firewire hard drives. |
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| Author: | pete-edworthy [ Tue Aug 23, 2005 9:53 am ] |
| Post subject: | |
Assuming its not the EPIA's fault, which it might be (see below), then kernel scheduling is the next stage to check. Run, as root; ps -eo nice,pid,cmd | less and look for squeezebox's server and mythbackend processes. They should both have a priority of 0 to start with. If they do try changing the squeezebox to be nice -1 (this will require being root) renice -1 <squeezebox server pid> If this solves the problem then 'Woop', other ideas are: you are playing mp3's? As any other format requires a lot more processor than 2%. is the squeezebox using wifi, and the mythbox on the same network? If so there is a very slim chance it’s network bandwidth. If all else fails blame VIA ;-}> It could well be a limitation of the EPIA, as they have been known to have DMA problems. VIA has patched the BIOS to prevent this. I don't know if that just means it is very conservative with switching DMA between devices; such as network, firewire, hd, graphics, tv-encoder card... which could cause the glitches. try playing the music of the internal hd, just copy a few tracks, and then see if the skip disapears. If it does it sounds like a problem with the EPIA platform or the firewire driver. Ideas: The squeezebox 2 looks even sexier, has 11g and a bigger buffer ;-}> If it is with the firewire hd; try a usb connection to the hd incase it is a driver issue. A linksys slug with a usb connection to the harddrive could probably run the squeezebox server. Well if nothing else it gives you a few places to look [/b][/list] |
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| Author: | tuatara [ Tue Aug 23, 2005 5:00 pm ] |
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Xsecrets wrote: I have no idea about running disks over firewire, however 24MB/s should be enough bandwidth. If it were an internal drive I would ask if dma was enabled on it properly, however I have no Idea how that work or if it works with firewire.
And a small correction RAID 1 is a mirror not a stripe set and does not help with performance. You are looking for RAID 0. However I doubt it will help in this instance. I would do some research on dma and firewire hard drives. Thanks for the note XSecrets. Oops - yes. I meant raid 0 / Striping. I want to increase throughput. Thanks. UDMA 5 is enabled on both drives. |
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| Author: | tuatara [ Tue Aug 23, 2005 5:17 pm ] |
| Post subject: | |
Hi Pete, pete-edworthy wrote: Assuming its not the EPIA's fault, which it might be (see below), then kernel scheduling is the next stage to check. Run, as root; ps -eo nice,pid,cmd | less and look for squeezebox's server and mythbackend processes. I'll check tonite, but I can say that when encoding, mythbackend uses 2% CPU. I dont think I'm CPU bound. pete-edworthy wrote: They should both have a priority of 0 to start with. If they do try changing the squeezebox to be nice -1 (this will require being root) renice -1 <squeezebox server pid> I'll give it a try - thanks. pete-edworthy wrote: you are playing mp3's? As any other format requires a lot more processor than 2%. is the squeezebox using wifi, and the mythbox on the same network? If so there is a very slim chance it’s network bandwidth. It is MP3, but I think the Squeezebox (SB) being sent the files raw by the server. SB Server never seems to go over a few % CPU, so I think its just a file copy over the network. I am using SB2s over 802.11g. While my actual throughput is lousy - I do get at least a MB/s. There is no other traffic at the time, and this only happens when the MBE is saving a program (my PVR-350 does the encoding). pete-edworthy wrote: If all else fails blame VIA ;-}> It could well be a limitation of the EPIA, as they have been known to have DMA problems. VIA has patched the BIOS to prevent this. I don't know if that just means it is very conservative with switching DMA between devices; such as network, firewire, hd, graphics, tv-encoder card... which could cause the glitches. Yes - I got wrapped up with a stack of people for many months on [url]href=http://forums.viaarena.com/messageview.aspx?catid=28&threadid=60131[/url] this forum as we tried to sort this one out. VIA ignored the problem for a year or so before coming out with the fix. I haven't applied it yet - my machine seems to be stable under debian/knoppmyth. I did get it stable under FC3 with 386 code gen turned on and LONGHAUL/CPUFREQ disabled. pete-edworthy wrote: try playing the music of the internal hd, just copy a few tracks, and then see if the skip disapears. If it does it sounds like a problem with the EPIA platform or the firewire driver.
Ideas: The squeezebox 2 looks even sexier, has 11g and a bigger buffer ;-}> If it is with the firewire hd; try a usb connection to the hd incase it is a driver issue. A linksys slug with a usb connection to the harddrive could probably run the squeezebox server. Well if nothing else it gives you a few places to look [/b][/list] It sure does. Thanks muchly for the feedback and ideas. Paul. |
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