Fredrick Posted September 26, 2017 Share Posted September 26, 2017 Hi, I'm trying to understand the iowait measurement, and afaik it means the processor waits on the drives to complete its operations. What I dont understand is why I'm getting iowait from preclearing drives? These are not part of the array/cache, and shouldnt be bothering the CPU during normal operations? Other than preclear there is not much going on atm. I've got several dockers that are just idling Quote Link to comment
Fredrick Posted September 27, 2017 Author Share Posted September 27, 2017 I'm bumping this. My preclear is now finished, but I'm still curious why this is. Controller-bottleneck? I dont see how with that little activity going on other than the preclear (which, granted, is heavy on the controller). I've got a LSI SAS 9201-16e HBA Quote Link to comment
unevent Posted September 27, 2017 Share Posted September 27, 2017 During preclear you are either writing to the drive as fast as it can or you are reading from the drive as fast as it can (it being the drive). The 'dd' command being executed is basically always waiting for the drive. Someone else can probably explain better. Quote Link to comment
Fredrick Posted September 27, 2017 Author Share Posted September 27, 2017 So it wouldnt slow down operations going to/from the array/cache? Quote Link to comment
unevent Posted September 27, 2017 Share Posted September 27, 2017 21 minutes ago, Fredrick said: So it wouldnt slow down operations going to/from the array/cache? Depends on what the operations are. Small stuff probably not noticeable. Quote Link to comment
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