OK, you are using high-end(-ish) drives. I find the un-cached result surprising as it appears to be higher than the result for the cached test. What are you using to do the test?
Also the very high cached read result (looks too high to me) would imply that the 512MB of RAM you have in the machine is having a large effect on the results. Could this be affecting the write tests also? Does the Adaptec card have a cache?
As for what you need for capture; I use a DC10+ that does mjpeg compression. At full resolution it uses 2GB every 5 minutes. This rounds up to 7MB/s. I don't know about your winnov card, but my DC10+ doesn't do that well on compression considering what mpeg1 and mpeg2 can do to it.
Anyway, so why such an interest in this xfs fs format?
Ed-T.
BTW, a single 5K RPM IDE just isn't good enough, and 7.5K RPMs aren't that much more expensive.
Jodie Reynolds wrote:
I think Eric has a point. Even with you calculations below, I think the
bottleneck is you hard drive. Write rate is slower than read rate.
13MB/s write rate for a single disk is doing very well.
Ed.-T.
I agree Write is slower than Read, but his numbers don't seem all that out
of the ball-park, depending on his drive.
testing my video capture box (Dual PIII-1Gig, 512Mb PC133 RAM, dual Quantum
Atlas 10,000 RPM drives (one disabled for test) w/29160 Adaptec SCSI-160
controller) I post numbers consistantly higher than 13MB/sec write, actually
rather substantially higher, more than double on a long sustained write
(like we'd see for video) -
Test File: "/$$test$$.tst"
Test File Size: 6400 MB
Testing Uncached Write Speed....
Data Transfer: 27.19 MB/s, CPU Load: 0.8%
Testing Uncached Read Speed....
Data Transfer: 21.89 MB/s, CPU Load: 0.4%
Testing Cached Write Speed....
Data Transfer: 17.89 MB/s, CPU Load: 2.0%
Testing Cached Read Speed....
Data Transfer:179.67 MB/s, CPU Load: 0.4% (PHEW!)
I'll also admit that this is skewed some-what out of the park of common
consumer machines... ! If we're talking about a 5400 RPM IDE-33 drive, all
bets are off. [grin]
But now on to the real question here for a moment: NTSC resolution is what,
480x704 x24bits x30fps (merged-frame/deinterlaced), right?
My numbers for full-screen, merged-frame/uninterlaced, non-hardware assisted
capture would then be 480 lines x704 pixels x24 bpp x30 fps or around
238Mbit/sec, which is about 30MBytes/sec, worst-case, right? Which would
explain why I like my winnov card doing 2:1 hardware compression taking me
down to about 15MByte/sec, or enough to reliably get the data onto the
drive.
Did I make some huge mistake here?
--- Jodie Reynolds, CTO
Interact Devices, Inc.
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