During normal operation, the LCD on an F7xx displays each second a number, which I believe to be the number of NFS operations in the last second, followed by a row of 0 to 10 splodges --- at any rate, I have never seen more than 10.
The LCD is 16 characters wide, and 5 digits of number, a space, and 10 blobs is 16 characters. (I guess we'll have to fix the code if we build a machine that can get the number above 99999.)
The hardware installation guide refers to this as "a bar graph" but doesn't go into details. What is actually being measured here? The number of splodges is correlated with the number, but not very strongly, and the number has a far larger dynamic range.
The bar graph scale varies over time to adapt to the load on the machine; see below.
After staring at that thing and wondering myself, it looks to me as if it is sort of a sliding rate-of-change meter.
When there is a big surge in #/Ops over a short period of time, bar jumps up a lot. Ditto for a big decrease in ops, shaving the bar.
The bar graph represents the ops/second on filers and, depending on the release, URLs/second or MBytes/second on NetCache boxes.
I.e., it's a bar graph of the number displayed on the line above it...
However, I've seen the bar nearly pegged with a relatively small number of ops (say, 400 or so) and hanging around 50% when the machine in question was pushing as many as I ever have seen it push.
However, the *scale* of the bar graph varies over time, so that if the machine is under low load, you don't have the bar graph pegged at "no blobs", and if it's under high load, you don't have it pegged at "all blobs", if the load is varying significantly.
The bar graph is scaled based on a maximum value, where:
the maximum value starts out at 100;
if the number to be displayed is greater than the max ops value, or if 5 seconds have passed since we last recomputed the max ops value, we compute the max ops value as the number to be displayed rounded up to a multiple of 100.
The "if the number to be displayed is greater than the max ops value" is to keep it from pegging at the right-hand edge under high load if the load is varying enough.
The "if 5 seconds have passed" is to keep it from pegging at the left-hand edge under low load, *and* to keep it from constantly bouncing back and forth if the load varies quickly between high and low.
In general, I think the main purpose is to have Cool Blinky Lights.
I see you have discovered the true secret of the bar graph.
- Guy "I just wish that, when I put the LCD support into ONTAP for 3.0, I'd put in the feature I'd wanted to put in, where it randomly puts, on occasion, 'Buy More Filers' into the LCD for a fraction of a second" Harris