Excellent guide, thanks!
In the "How to Increase Raid Rebuild/Expansion Speed" section, you had a disclaimer that you hadn't seen any reports of anyone trying it.
For that reason I want to give you my account.
I have a TS-509 with v2.1.0 Build 1202.
I had a RAID-5 array with four 1TB WD drives (WD1002FBYS-01A6B03.0), and I added a fifth using "Add Drive" on the "RAID Management Tool" page.
Before I started that process I shut off all services (multimedia station, download station, web server, rTorrent++, etc...).
I understand that you're supposed to be able to access the data while it's expanding, but I'm totally new to RAID and I was a bit apprehensive about it.
So I took the "better safe than sorry" approach and did not access the NAS RAID drive at all during the expansion process.
After about 12 hours of expanding it was at 3%, which put it on par to complete in 8 or 9 days.
I then found the article on how to speed it up.
I logged in with Putty and found that the speed limit min and max were set to the default values:
# cat /proc/sys/dev/raid/speed_limit_min
Using "cat /proc/mdstat", I saw that the expanding speed was right around 1 to 1.5MB per second.
I used "echo 10000 >/proc/sys/dev/raid/speed_limit_min" to up the speed to 10MB per second.
Looking at "cat /proc/mdstat" again, I saw that within a time span of about a minute or so, the speed gradually increased to about 10MB per second.
I then used "echo 25000 >/proc/sys/dev/raid/speed_limit_min" in an attempt to up the speed to 25MB per second.
However I never saw anything above a speed of about 11MB per second.
I'm not certain if it reached a limit of how fast it could go, or if it only responds to the first speed_limit_min change.
The CPU usage was about 8-10% and the HDD, CPU and System temperatures never increased.
The temps were between 27-30C (80-86F) for the HDD and System, and about 19C (66F) for the CPU.
The ambient temp probably was around 13C (55F). (I have my NAS in an equipment rack in the basement).
After about 38 hours the process completed successfully.
If I had immediately increased the speed_limit_min to 10MB per second, I think the total time would have been around 27 hours.
Below are the entries it made in the log.
Note that where is says "Rebuilding done" is the 50% mark on the "Device Configuration - SATA Disk" web page, so the last 50% only took about 1.5 hours.
2009-01-14 10:06:04 System 127.0.0.1 localhost [RAID5 Disk Volume: Drive 1 2 3 4 5] Expanding Raid Device completed.
2009-01-14 10:06:04 System 127.0.0.1 localhost [RAID5 Disk Volume: Drive 1 2 3 4 5] Expanding Raid Device completed. Drive 5 is added.
2009-01-14 08:32:49 System 127.0.0.1 localhost [RAID5 Disk Volume: Drive 1 2 3 4 5] Rebuilding done.
2009-01-12 20:17:35 System 127.0.0.1 localhost [RAID5 Disk Volume: Drive 1 2 3 4 5] Start rebuilding.
2009-01-12 20:17:31 System 127.0.0.1 localhost [RAID5 Disk Volume: Drive 1 2 3 4] Start to expand Raid Device: Add Drive 5.