chore: imported articles from the private kb

knowledge base/dd.md

@@ -4,8 +4,24 @@ Convert and copy a file.
 
 ## TL;DR
 
+N and BYTES values may be followed by the following multiplicative suffixes:
+
+| suffix      | multiplication      |
+| ----------- | ------------------- |
+| `c`         | 1                   |
+| `w`         | 2                   |
+| `b`         | 512                 |
+| `kB`        | 1000                |
+| `K`         | 1024                |
+| `MB`        | 1000 * 1000         |
+| `M` or `xM` | 1024 * 1024         |
+| `GB`        | 1000 \* 1000 * 1000 |
+| `G`         | 1024 \* 1024 * 1024 |
+
+and so on for T, P, E, Z, Y.
+
 ```sh
-# Read 512 random Bytes for each iteration and save them .
+# Read 512 random Bytes for each iteration and save them.
 dd if='/dev/urandom' of='output/file' count=2 bs=512
 
 # Read 1000 Bytes for each iteration and save them while watching the progress.
@@ -26,11 +42,54 @@ dd if=/dev/drive_device of=path/to/file.img status=progress
 
 # Restore a drive from an IMG file and show the progress:
 dd if=path/to/file.img of=/dev/drive_device status=progress
+
+# Create images from disks.
+sudo dd if=/dev/mmcblk0 of=/tmp/mmcblk0.img conv=sync bs=4k
+sudo dd if=/dev/sda conv=sync,noerror bs=64K | gzip -c > /mnt/sdb/disk.img.gz
+
+# Write an image to disk.
+sudo dd if=/tmp/mmcblk0.img of=/dev/mmcblk0 conv=fsync oflag=direct bs=4M status=progress
+
+# Clone a disk on another disk.
+sudo dd if=/dev/sda of=/dev/sdb conv=fsync bs=4M oflag=direct status=progress
 ```
 
+## Benchmark disks
+
+Use:
+
+- a single, bigger file for throughput (write speed)
+- multiple, smaller files for latency
+
+```sh
+dd \
+  if=/dev/input.file of=/path/to/output.file \
+  bs=block-size count=number-of-blocks \
+  oflag=dsync status=progress
+```
+
+Examples:
+
+```sh
+dd if=/dev/zero of=/tmp/test1.img bs=1G count=1 oflag=dsync
+dd if=/dev/zero of=/tmp/test2.img bs=64M count=1 oflag=dsync
+dd if=/dev/zero of=/tmp/test3.img bs=1M count=256 conv=fdatasync
+dd if=/dev/zero of=/tmp/test4.img bs=8k count=10k
+dd if=/dev/zero of=/tmp/test4.img bs=512 count=1000 oflag=dsync
+```
+
+## Further readings
+
 ## Sources
 
-- [cheat.sh]
+All the references in the [further readings] section, plus the following:
 
+- [cheat.sh]
+- [Linux and Unix Test Disk I/O Performance With dd Command]
+
+<!-- project's references -->
+<!-- internal references -->
 <!-- external references -->
 [cheat.sh]: https://cheat.sh/dd
+[how to create a disk image in linux]: https://itstillworks.com/clone-hard-drive-ubuntu-6884403.html
+[linux and unix test disk i/o performance with dd command]: https://www.cyberciti.biz/faq/howto-linux-unix-test-disk-performance-with-dd-command/