In a message dated: Fri, 20 Dec 2002 09:52:53 EST Michael O'Donnell said: >I'm not sure I understand what you're trying to measure,
I want to know what percentage of time the disk is busy doing stuff. Or, conversely, what percentage of time the disk is not doing stuff. Here's the problem set. I/We have this box being used as a black-box storage device. We are trying to characterize it's over-all performance; from CPU utilization to disk IO, memory, swapping, etc. Since most of the people I work with are hard-core storage engineers, one of the metrics they're used to is "disk busy time", that time that the disk is spent doing something, and therefore is unable to take more requests. The interesting thing is that iostat will tell you how many requests per second were made, and how much data per second was transferred, but there is no correlation between the two; i.e. I know how many requests were made, but not the size of those requests. Therefore, I have no idea what percentage of requests is represented by the amount of data transferred. mod> you might find it difficult to characterize certain behaviors mod> of your disk units if they have caches (pretty much all of mod> them do) that are enabled (pretty much all have them enabled mod> by default) because the caches will, to some extent, hide the mod> delays due to seek- and rotational-latencies. Well, yes, I understand that, however at this level, I don't think it matters. The OS should only care how fast it's requests are answered. If the OS makes a request, and it gets blocked, then the disk is "busy". On the other hand, if it makes a request, and gets and answer, the disk wasn't "busy". Some answers are obtained faster than others, which might be attributable to cache hits, but the bottom line is, the disk wasn't busy when I made my request. (btw, I too question the validity of such a number, but hey, that's what they asked me for, and they pay me, so I need to humor them :) -- Seeya, Paul -- Key fingerprint = 1660 FECC 5D21 D286 F853 E808 BB07 9239 53F1 28EE It may look like I'm just sitting here doing nothing, but I'm really actively waiting for all my problems to go away. If you're not having fun, you're not doing it right! _______________________________________________ gnhlug-discuss mailing list [EMAIL PROTECTED] http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss