IBM Support

Thermals in a FlashSystem

Question & Answer


Question

How does the FlashSystem monitor and react on temperature changes?

Cause

The FlashSystem has environmental specifications regarding its operating and non-operating temperature. This specification is documented in the Product Guide. As example for the FlashSystem 900:


Air temperature:

  • Operating: Minimum of 5°C (50°F) at 30.5 m below to 3,000 m above sea level (100 ft below to 9,840 ft above); Maximum rated up to 40°C (95°F) at 30.5 m below to 950 m above sea level, de-rated 1°C for each 225 m above 950 m up to 3,000 m
  • Non-operating: (AE1/AE2 hardware): -10°C to 50°C (14°F to 125°F)
  • Non-operating: (AE3 hardware) -40'C - 50'C (-40'F - 122'F)


source: http://www.redbooks.ibm.com/abstracts/tips1261.html


The FlashSystem has an internal mechanism to control the temperature in the specific operating range and reacts when this range is left. This tip will explain this internal behavior.

Answer

The FlashSystem actively manages fan speeds to keep the system in a normal thermal range. Further it has a control limit which is a limit set to ensure the system is under normal operation. When this limit is reached, the fans will increase the speed to provide more air flow for cooling. If the system gets into a warning temperature, it send an alert to notify that the system is getting too warm. Also, once the fans are running at maximum speed, the IBM FlashSystem will throttle the I/O to try to prevent the temperature from climbing further up.

If the temperature continues to rise and the system reaches a critical temperature, it will gracefully shutdown.

The IBM FlashSystem does protect itself from faulty sensors with two methods. It will discard temperature readings which are outside of a reasonable range. This prevents it from taking down the system due to a faulty sensor. It also performs what is called "windowing" which means that it will require a reading to be present for a period of time before taking an action. This protects against transient readings or occasional glitches. The temperature must be in a range for a sustained period of time before it will react.

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Document Information

Modified date:
17 February 2023

UID

ssg1S1010534

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