How to diagnose disk access lag/freeze?

[benjatelcom]

I want to test my raid array, I think that disk access temporarily halts and resumes again, causing a glitch in playback.

Any ideas about a test that could bag this kind of error?

[jerryt]

HDtach

[lotusvball]

I would be very interested in this if you find a solution. I have all of my DVD's on a raid 5 aray and I get a hicup/freeze every 10 minutes or so.

[jerryt]

Originally Posted by lotusvball

I would be very interested in this if you find a solution. I have all of my DVD's on a raid 5 aray and I get a hicup/freeze every 10 minutes or so.

Be sure drive indexing is off.

[benjatelcom]

HD Tach doesnt seem to show any lag, are we sure it will properly identify if drive access halts for a split second and then resumes?

Logged 201MB/sec burst with HD Tach, on my 5400RPM drives. The trend was pretty spikey, but I never saw it bottom out like it was waiting for data from an unresponsive array.

[jerryt]

201mb/sec burst is not a very good number.

Four hard drives in raids should be much better.

A dip in the sequential read speed as seen here (h**p://forum.pcstats.com/showthread.php?t=41317)
in post #3 is what you want to look for as a hang in reading. But your read speed is the first problem.

[benjatelcom]

It looks like I should be testing with IOmeter instead of HDTach. I don't have any comparisons to make with the raid configuration I have now, but I am looking at a few right now. Since an HD stream needs 1 to 4MB/sec I thought these numbers should be sufficient.

-Edit: My drives are slow 5400RPM drives, so that could play a factor + raid 5.

[motobarsteward]

About six months ago, I started having glitch and pause problems on my capture drive. I run a couple of raids (0.6T and 2T) and, then, a 320Gig drive just dedicated to capture. I had problems with playback freezing at about 8.30pm at night for a couple of seconds and 'broken' mpg2 files. Sage played them but I couldn't make a DVD with them or anything. Eventually, after re-installing windows and rebuilding the server, I began to suspect the drive its self. I ran every diagnostic on it I could find and everything came back OK. I swapped the cables with no success. In the end, I through some money at the problem and bought a new drive. All my problems went away. The old drive had a nasty accident with a big hammer.