Wynik polecenia iostat-dmx /dev/sda1 3
util% - im wyższy - tym gorzej , znaczy że dysk jest mocno zutylizowany (duży ruch I/O). Jesli ciągle przekracza 80% należy rozważyć rozbudowę/zmianę RAID
w/s - zapisy na sekundę
r/s - odczyty na sekundę
svctm - czas obsługi requesta zapisu lub odczytu. Im większa wartość tym gorzej, znaczy że system ma długi czas obsługi requesta :(((
Powyższe wartości składają się na wyliczenie UTIL% = (r/s + w/s) * svctim / 1000ms * 100
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- (await-svctim)/await*100: The percentage of time that IO operations spent waiting in queue in comparison to actually being serviced. If this figure goes above 50% then each IO request is spending more time waiting in queue than being processed. If this ratio skews heavily upwards (in the >75% range) you know that your disk subsystem is not being able to keep up with the IO requests and most IO requests are spending a lot of time waiting in queue. In this scenario you will again need to take any of the actions above
- %iowait: This number shows the % of time the CPU is wasting in waiting for IO. A part of this number can result from network IO, which can be avoided by using an Async IO library. The rest of it is simply an indication of how IO-bound your application is. You can reduce this number by ensuring that disk IO operations take less time, more data is available in RAM, increasing disk throughput by increasing number of disks in a RAID array, using SSD (Check my post on Solid State drives vs Hard Drives) for portions of the data or all of the data etc
