What are the chances to recover a NAS device using Linux OS?

At www.nasrecovery.info you are offered to use Linux as a first thing to recover NAS. In practice, it does not work at all or at least you cannot obtain any meaningful results.

Let's give an example - sometimes happens that you assemble an array by means of md-raid driver in VMware only to see that one member disk has dropped out after restart. Although it is well-known that VMware provides infinitely reliable virtual hardware, so the only option remains is that md-raid is buggy. Thus, there is very little chance to assemble the array with valuable data with the help of Linux. Keep in mind, that it makes sense to try at least several different Linux versions for, as of now, quite a number of Linux distributions are available at the official Linux web site.

By the way, some of you will be lucky, although it is not mentioned on www.nasrecovery.info - some NASes do work on Win Embedded.

NAS and backup power

I saw at www.raidtips.com an interesting post "Test your RAID" where it is recommended to pre-test fault tolerance.  One of the suggested approach to test fault tolerance is to do a simulated power failure.
However, just turning off the power is not enough to test an UPS. In normal operation NAS receives the notifications from its UPS unit continuously and takes action immediately. However, when starting up the reports concerning power failure are not received. On top of that one should consider that the entire cycle (from start up to shut down) may require up to ten minutes.

Let's consider such a situation:

1. suddenly power fails,
2. your NAS unit takes power from the battery for some time and then shuts down,
3. the grid power comes back and NAS begins to start up,
4. at this moment power fails again.

Now NAS is not able to process a report on power failure event until it fully starts up. As soon as Network Attached Storage loads, it detects that the power failure has occurred and starts to shut down.
But it may happen that the system will not be able to shut down correctly since UPS doesn't supply power long enough due to battery exhaustion (during the first cycle).
One can avoid this by setting the NAS up so that it finishes its work as soon as it receives a message that power failure occurs. Doing this one can save enough charge of battery for another start-stop cycle.
Also you can configure Network Attached Storage in such a way that NAS does not restart automatically, but manually after the power failure has occurred.

In what cases you need to measure the performance of your hdd.

If you think that the storage device has poor performance, first you need to get data on linear read speed, disk access time, and IOPS (I/O operations per second) for the data storage device in question.

All this information can be collected with the help of any benchmark tool for storage devices. There exist paid and not benchmark software. I used free and easy-to-use benchmark software - BenchMe that shows linear read speed in real time. The free benchmark tool also produces a chart with distribution of access time determined for the storage device. BenchMe displays features the data storage device supports as well.

On the developer's site one can find sample benchmark charts made by BenchMe for various data storage devices - typical hard drives, SSDs, and RAID arrays.
The only disadvantage I come across is that the tool doesn't handle hard disks connected via USB.