The bootup process involves three stages: (please see post #255 for more details).
- Hardware enumeration to enable the OS loader to take control
- Main Boot Path Time - Essential services and drivers to load desktop
- Post boot time - Drivers, processes and applications that arenít critical for user interaction and can be loaded with low-priority I/O that always gives preference to user-initiated actions that execute using normal I/O priority.
By default the hIOmon software is configured to automatically begin monitoring when the services are started during stage three. There is also an option, however, whereby the hIOmon software can be configured so that it instead begins monitoring very early within the "Main Boot Path Time" (stage 2). Please see post #32 for details
The amount of data loading during the boot process can vary significantly depending on the type of applications that have been installed. The time it takes to fully load can also vary significantly depending on user-initiated actions, automatic updates and AV activity.
During boot all the data has to initially be read from the physical disk.
Typical read transfer sizes during boot can be found in post #190. The vast amount of read transfer sizes are 6,000 bytes and below. Only 16 read transfer sizes were above 1MB and the largest read transfer sizes was 11MB.
The boot process was monitored on three different storage systems. HDD, SSD & SSD Raid 0 (please see post # 105). Key storage load metrics (approximated)
Key storage performance metrics
- 95% random reads and writes.
- 20,000 I/O operations overall.
- Overall average IOPs = 190
- Overall average transfer size 20,000 bytes (19KB)
- Total read data transferred 420MB
- Total write data transferred 24MB
- HDD Percentage of fast read/write IOPs performed = 1.2%
- SSD Percentage of fast read/write IOPs performed = 98.3%
- SSD Raid 0 Percentage of fast read/ write IOPs performed = 98.9%
- HDD busy time = 1min 58s
- SSD busy time = 8.54s
- SSD Raid 0 time = 6.59s
- HDD average response time = 53.40ms
- SSD average response time = 0.49ms
- SSD Raid 0 average response time = 0.33ms
Whilst the performance difference between HDD & SSD is significant the difference between a single SSD and SSD Raid 0 is marginal. (Source