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I/O Problem? Video Streaming too slow
Is my HDD slowing my streaming speed?
alexelisenko




msg:4003199
 8:15 pm on Oct 7, 2009 (gmt 0)

Hello All,

I have a bit of a problem that I cant seem to figure out.

I have a media hosting site, and its on a 1000Mbit connection,
I originally had 2 x 1.5TB SATA Drives hosting the .flv files, but with around 1500 concurrent streams from hundred of different files, I would only use maybe 80Mbit of my available port speed.

I checked my usages in OS (CentOS), iostat showed my drives at 95% util and 55% await, which is not good if I understand it correctly. My first thought was, I need a faster HDD, so I upgraded to SAS(Serial Attached SCSI) which is a good 15,000RPM and can also do multiple operation with one rotation of the disk.

After this upgrade I am getting 100Mbit max, and iostat shows 97% util. with 1500 streams, 100Mbit makes for a very crappy user experience, since it takes 3 times longer to buffer the video than to watch it.

I was hopping someone here can give me a new direction to go in. Here are my server specs.

INTEL-Core2Duo-8400
8GB RAM
1 x 300GB SAS 15,000RPM ** Media Files are here
2 x 1.5TB SATA 7,200RPM ** website here

Running: PHP, MySQL, Httpd on Apache
FLV Streaming: Lighttpd w/ mod_flv_streaming

Please let me know of your thoughts,

Thanks in advance!

 

vincevincevince




msg:4006319
 3:49 pm on Oct 13, 2009 (gmt 0)

Your drives are too big. You need a larger number of smaller drives, each with their own controller. One drive cannot possibly pull so many different streams concurrently as it spends too long jumping between files.

alexelisenko




msg:4007603
 3:06 pm on Oct 15, 2009 (gmt 0)

That sounds like the problem, but I was very surprised that switching to SAS from SATA gave such a low performance boost. SAS is supposed to perform multiple reads per rotation but not much benefit in actual throughput.

So you're suggesting a RAID setup? or just dropping in more drives and reworking the script to keep track of what files are where?

I was also considering a SSD drive, what are your thoughts?

vincevincevince




msg:4008550
 1:01 am on Oct 17, 2009 (gmt 0)

It is going to depend on your usage pattern. Are we talking just a few media files which have many simultaneous connections, or a large number of files with connections spread across them? The first case may favour a serious bulking of your RAM and buffering as much as you can there.

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