
UFS-Impaired-Storage
====================

Contents
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1. Overview
2. Quick reference guide
3. Detailed information

1. Overview
-----------

Flash storage performance can be degraded over time due to the storage and
file system aging as well as complicated internal structure.
Impaired Storage emulate degraded storage latencies by adding delay for each
I/O request.


2. Quick reference guide
------------------------

* Case1: delay all read requests by 1.5x
  echo 150 > /sys/.../impaired/read_delay_percent
  echo 1 > /sys/.../impaired/enabled

* Case 2: delay all write requests by 300us
  echo 300 > /sys/.../impaired/write_delay_us
  echo 1 > /sys/.../impaired/enabled

* Case 3: delay both read and write requests by 2x, then add 100us
  echo 200 > /sys/.../impaired/read_delay_percent
  echo 200 > /sys/.../impaired/write_delay_percent
  echo 100 > /sys/.../impaired/read_delay_us
  echo 100 > /sys/.../impaired/write_delay_us
  echo 1 > /sys/.../impaired/enabled

* Case 4: emulate impaired read latencies.
  echo fragftl > /sys/.../impaired/read_model
  echo 1 > /sys/.../impaired/enabled


3. Detailed information
-----------------------

http://go/impairedstorage