Performance and reliability
ScramFS has been tuned for performance, designed for security and engineered for reliability. It's carefully designed to hit the sweet spot to achieve all three.
High performance – the benchmarks show it
ScramFS has been designed to run on a range of hardware in different environments – from high performance servers to low performance embedded devices.
The performance benchmarks demonstrate a level of overhead that is barely perceptible to users. That’s why we can call our transparent.
Fast sustained reads and writes - for large records
Sustained write performance benchmarking: open a file for writing, write 1GiB, close it.
| Test environment | Time taken | Encrypt and write speed |
|---|---|---|
| 2014 MacBook Pro 15" with 2.2GHz Core i7 processor | 3.09s | 347MB/s |
| 2014 MacBook Pro 13" with 2.6GHz Core i5 processor | 4.53s | 237MB/s |
| 2015 MacBook with 1.2GHz Core M processor | 4.29s | 250MB/s |
| 2017 Acer Apire 5 with 1.6GHz Core i5 processor | 1.78s | 603MB/s |
| Raspberry Pi 3 | 40.12s (300MB) | 8.25MB/s |
Sustained read performance benchmarking: open a file for read, read 1GB, close it.
| Test environment | Time taken | Read and decrypt speed |
|---|---|---|
| 2014 MacBook Pro 15" with 2.2GHz Core i7 processor | 2.91s | 369MB/s |
| 2014 MacBook Pro 13" with 2.6GHz Core i5 processor | 4.13s | 260MB/s |
| 2015 MacBook with 1.2GHz Core M processor | 3.90s | 275MB/s |
| 2017 Acer Apire 5 with 1.6GHz Core i5 processor | 1.65s | 651MB/s |
Note: hardware has been chosen to obtain accurate results that measure encryption and decryption throughput, not the actual limitations of the hardware. For example, running ScramFS on a USB connected 2.5 inch hard drive will often limit throughput to around 80MB/s. Because ScramFS can often run at many times that speed, the overheads become imperceptible to the user.
Fast saving and loading of data - for small records
Open, write 64KiB, close a file, and repeat for 1000 files.
| Test environment | Time taken | Files saved per second |
|---|---|---|
| 2014 MacBook Pro 15" with 2.2GHz Core i7 processor | 1.80s | 556 files per sec |
| 2014 MacBook Pro 13" with 2.6GHz Core i5 processor | 2.47s | 405 files per sec |
| 2015 MacBook with 1.2GHz Core M processor | 2.88s | 347 files per sec |
| 2017 Acer Apire 5 with 1.6GHz Core i5 processor | 1.01s | 990 files per sec |
Open, read 64KiB, close a file, and repeat for 1000 files.
| Test environment | Time taken | Files loaded per second |
|---|---|---|
| 2014 MacBook Pro 15" with 2.2GHz Core i7 processor | 1.14s | 877 files per sec |
| 2014 MacBook Pro 13" with 2.6GHz Core i5 processor | 1.17s | 854 files per sec |
| 2015 MacBook with 1.2GHz Core M processor | 1.57s | 637 files per sec |
| 2017 Acer Apire 5 with 1.6GHz Core i5 processor | 0.75s | 1333 files per sec |
Fast directory listing
Performance benchmark: listdir on a directory with 10,000 files in it. Measures file name decryption speed.
| Test environment | Time taken | File names decrypted per second |
|---|---|---|
| 2014 MacBook Pro 15" with 2.2GHz Core i7 processor | 1.79s | 5600 files names / sec |
| 2014 MacBook Pro 13" with 2.6GHz Core i5 processor | 1.65s | 6060 file names / sec |
| 2015 MacBook with 1.2GHz Core M processor | 2.09s | 4770 file names / sec |
| 2017 Acer Apire 5 with 1.6GHz Core i5 processor | 1.12s | 8929 file names / sec |
Reliability and robustness
Developing a reliable and robust file system is a huge challenge.
We’ve run ScramFS through a comprehensive battery of stress tests in many different environments, throwing massive amounts of data at it, and simulating the most high-load situations we could imagine.
We will publish the results of our tests in the coming weeks.
