Burning ISOs to USB sticks on Mac / OS X

For some reason i cannot get the easy-to-use tools out there for burning ISOs to work… Command line to the rescue:

First, make sure Homebrew is installed. It is strictly not needed for the burning-to-thumb-drive process, but will enable the progress indicators, which are quite nice to have for long running tasks. Now install Pipe Viewer from Homebrew:

[code language=”bash”]

$ brew install pv

[/code]

Now we need to figure out the device name of our USB drive. In a terminal window (you are using iTerm2 – right? Infinitely better than OS X built in Terminal app):

[code language=”bash”]

$ diskutil list

#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *251.0 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_HFS Macintosh HD 250.1 GB disk0s2
3: Apple_Boot Recovery HD 650.0 MB disk0s3
/dev/disk1
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *320.1 GB disk1
1: EFI EFI 209.7 MB disk1s1
2: Apple_HFS SSD backup 180.0 GB disk1s2
3: Apple_HFS Temp 139.6 GB disk1s3
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk2
1: EFI EFI 209.7 MB disk2s1
2: Apple_HFS Macken_Ext Backup 999.9 GB disk2s2
/dev/disk3
#: TYPE NAME SIZE IDENTIFIER
0: FDisk_partition_scheme *8.0 GB disk3
1: DOS_FAT_32 WHEEZY 8.0 GB disk3s1
$

[/code]

/dev/disk3 is the USB thumb drive. I previously had another Wheezy image on it, thus its name.

Now unmount it:

[code language=”bash”]

$ diskutil unmountDisk /dev/disk3
Unmount of all volumes on disk3 was successful
$

[/code]

Nice. Now let’s write the ISO to the drive:

[code language=”bash”]

$ pv -petr ~/Desktop/debian-7.2.0-amd64-DVD-1.iso | sudo dd of=/dev/disk3 bs=128k
Password:
0:00:38 [4.94MiB/s] [====>                  ] 3% ETA 0:16:55

[/code]

Now let’s wait. Looks like it will take approximately another 17 minutes..

When done, just eject the thumb drive as usual, remove it and you have a bootable Debian install drive. Mission accomplished.

Netgear RN312 firmware upgrade 6.0.8 to 6.1.2

RN312 6_1_2 available

Seems Netgear just released firmware version 6.1.2 for those products that support the new UI (I believe UltraNAS and other non-Intel based devices does not get the benefits of the new version 6 and above firmware – or maybe they have reconsidered – not sure).

Updating is always a bit scary when you have a smoothly running system, but after reading the release notes they mainly covered more high end devices (as compared to the RN312 that I have), so why not..

I believe the upgrade went well, all the applications I have installed myself (CrashPlan, Monitorix etc) seems to be work ok.

RN312 6_1_2 installed.png

 

 

 

Moving CrashPlan cache and log directories to new locations

As discussed in a previous post, the ReadyNAS might run out of disk space on the 4 GB root partition if you install software other than that provided by NetGear.

In my case it was CrashPlan’s cache and log files that were filling up the root partition, with warning emails every 10 minutes that 81% of the root partition was used, 82%… 83%…, so they needed a new home. Turns out it is not too hard:

ssh into the NAS, then su to become root. Stop CrashPlan (if it is running):

[code language=”bash”]
root@RN312:/home/admin# service crashplan stop
Stopping CrashPlan Engine … OK
root@RN312:/home/admin#
[/code]

Make a copy of CrashPlan’s configuration file, in case something goes wrong:

[code language=”bash”]
root@RN312:/home/admin# cp /usr/local/crashplan/conf/my.service.xml /usr/local/crashplan/conf/my.service.xml.orig
root@RN312:/home/admin#
[/code]

Take a look at CrashPlan’s cache directory:

[code language=”bash”]
root@RN312:/home/admin# ls -lah /usr/local/crashplan/cache/
total 40M
drwxr-sr-x 1 root staff  106 Sep 25 03:00 .
drwxr-sr-x 1 root staff  258 Sep 25 21:31 ..
drwxr-sr-x 1 root staff  170 Sep 25 21:31 42
-rw-r–r– 1 root staff 8.4K Sep 25 21:31 cpft1_42
-rw-r–r– 1 root staff 1.9K Sep 25 21:31 cpft1_42i
-rw-r–r– 1 root staff 2.1K Sep 25 21:31 cpft1_42x
-rw-r–r– 1 root staff  23M Sep 25 21:31 cpgft1
-rw-r–r– 1 root staff 8.8M Sep 25 21:31 cpgft1i
-rw-r–r– 1 root staff 7.9M Sep 25 21:31 cpgft1x
-rw-r–r– 1 root staff  986 Sep 25 03:02 cpss1
root@RN312:/home/admin#
[/code]

Create cache directory in new location:

[code language=”bash”]
root@RN312:/home/admin# mkdir /home/admin/from_root/crashplan/cache
[/code]

Change the config file to point to the new location (using your favourite editor, vim used here):

[code language=”bash”]
root@RN312:/home/admin# vim /usr/local/crashplan/conf/my.service.xml
[/code]

Change
<cachePath>/usr/local/crashplan/cache</cachePath>
to
<cachePath>/home/admin/from_root/crashplan/cache</cachePath>

(Adjust as needed if you have selected some other place for the CrashPlan files.)

Now move the cache files:

[code language=”bash”]
root@RN312:/home/admin# mv /usr/local/crashplan/cache/* /home/admin/from_root/crashplan/cache/
root@RN312:/home/admin#
[/code]

Time to move CrashPlan’s log files. They are originally stored in /usr/local/crashplan/log/, let’s move them to /home/admin/from_root/crashplan/log.

[code language=”bash”]
root@RN312:/home/admin# ls -lah /usr/local/crashplan/log/
total 111M
drwxrwxrwx 1 root staff  346 Sep 23 04:41 .
drwxr-sr-x 1 root staff  258 Sep 25 21:31 ..
-rw-r–r– 1 root root   33K Sep 25 21:31 app.log
-rw-r–r– 1 root root   23M Sep 25 21:31 backup_files.log.0
-rw-r–r– 1 root root   26M Jul 12 19:50 backup_files.log.1
-rw-rw-rw- 1 root root     0 Aug 15 15:21 engine_error.log
-rw-r–r– 1 root root  6.4K Sep 25 21:31 engine_output.log
-rw-r–r– 1 root root  180K Sep 25 21:31 history.log.0
-rw-r–r– 1 root root  501K Sep 17 13:47 history.log.1
-rw-r–r– 1 root root  501K Aug 25 08:10 history.log.2
-rw-rw-rw- 1 root root     0 Aug 15 15:24 restore_files.log.0
-rw-r–r– 1 root root   13M Sep 25 21:31 service.log.0
-rw-r–r– 1 root root   26M Sep 23 04:41 service.log.1
-rw-r–r– 1 root root   26M Sep 17 14:35 service.log.2
root@RN312:/home/admin#
root@RN312:/home/admin# mkdir /home/admin/from_root/crashplan/log
root@RN312:/home/admin#
[/code]

Find the fileHandler tags (there are 4 of them dealing with log files), modify them so they point to the new log directory. So, once again edit /usr/local/crashplan/conf/my.service.xml.orig, part of mine looks like this after moving the log files. Change the paths as neeed for your choice of new directories:

[code language=”bash”]
<serviceLog>
    <fileHandler append="true" count="2" level="ALL" limit="26214400" pattern="/home/admin/from_root/crashplan/log/service.log"/>
  </serviceLog>
  <serviceErrorInterval>3600000</serviceErrorInterval>
  <historyLog>
    <fileHandler append="true" count="10" level="ALL" limit="512000" pattern="/home/admin/from_root/crashplan/log/history.log"/>
  </historyLog>
[/code]

Start CrashPlan again:

[code language=”bash”]
root@RN312:/home/admin# service crashplan start
Stopping CrashPlan Engine … OK
root@RN312:/home/admin#
[/code]

And finally check free disk space on /:

[code language=”bash”]
root@RN312:/usr/local/crashplan/log# df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs          4.0G  1.7G  1.8G  49% /
tmpfs            10M  4.0K   10M   1% /dev
/dev/md0        4.0G  1.7G  1.8G  49% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           2.0G  5.8M  2.0G   1% /run
tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup
tmpfs           2.0G     0  2.0G   0% /media
/dev/md127      2.8T  1.1T  1.7T  39% /data
/dev/md127      2.8T  1.1T  1.7T  39% /home
/dev/md127      2.8T  1.1T  1.7T  39% /apps
root@RN312:/usr/local/crashplan/log#
[/code]

49% – nice!

Installing Debian on old ASUS motherboards

Having a couple of decommissioned ASUS motherboards (M2NPV-VM and A8N-VM CSM), as well as a 19″ cabinet with ATX cases in it, they could together be a setup for lab work, trying out Linux server stuff, as a test bed for network gear etc.

Installing Linux (Debian) is usually pretty easy, a couple of snags along the way though.
So, note to self: read this if these motherboards need to be reinstalled sometime. It will save you/myself some time.

Booting from USB flash disk

  1. The BIOS of both boards need to be changed so that the flash disk is 1st disk (before the SSD also installed), and also 1st in boot order. Otherwise it will not boot from the thumb drive.
  2. Install Debian as usual.
  3. Once you get to the GRUB installation part of Debian install, follow the default setting and install to first disk. Which is the flash thumb drive, I know. But trying the get the Debian installer to install GRUB anywhere else just failed consistently – I have no idea why. Should have worked to install it to /dev/sdb (which is the SSD).
  4. Reboot into recovery mode with the thumb drive still inserted (as GRUB was installed to it. remember?). You should now end up in a command line shell.
  5. Do a “grub-install /dev/sdb” to install GRUB to the SSD. The devices might be different depending on the installed hardware, check with “ls /dev”, “du” and related commands, to get the device name of the SSD
  6. Reboot, quickly remove the thumb drive during the reboot, and GRUB should now appear, served from the SSD.

 

Windows 8 and Debian Wheezy dual boot

An old Dell XPS M1330 laptop has been collecting dust around here for ages. It’s one of those “yes… I am sure that laptop will come in handy some day…” machines, and I finally took the time to set it up as test machine for Windows 8 and Linux. I also had an unused SSD drive that could replace the old and slow HD in the laptop.

Time to get to work!

Install Windows 8

  1. Get the Windows 8 installer. Run it, then go through all the steps until you get an option to “Install by creating media”. A Windows machine of some kind obviously needed for this. This will create a bootable USB flash drive or an ISO, with all the Windows install files on it.
  2. You can actually install Windows 8 directly from the flash drive, but once you try to activate Windows it will tell you that the product key can only be used for upgrades. I found this out the hard way -> had to re-do the whole process.
  3. Get a copy of Windows XP, Vista or whatever earlier Windows version you can find. I happened to have a bunch of XP Pro licenses taken from old computers over the years. If going the XP route, it might be worth installing from XP SP3 (rather than SP2 or earlier), IIRC the pre-SP3 XP versions were rather crappy.
  4. Windows XP + SSD = <FAIL>. As the Windows 8 license was an upgrade, I had to get some prior Windows version installed first. Turned out that Win XP SP3 didn’t play nicely with the SATA2 SSD I had installed. Probably some missing drivers in the XP installation – SATA2 just had not been invented when Win XP was hot, I guess.
    I had to change a couple of BIOS parameters handling flash cache and SATA emulation (reverting back to some older ATA variant, I believe. Not sure, but it worked).
    The XP installer then detected the SSD and fired up as expected.
  5. Install XP from CD/DVD, as was done in the old days. No need to apply updates etc once it is installed. I didn’t activate Windows XP Genuine Advantage either.
  6. While in XP, start the Windows 8 installer from the flash drive created step 1 above. From here it’s a pretty easy ride, think I went with the defaults most of the way
  7. Windows 8 should then be installed, and XP gone. Nice.

If you have a fresh-install product key for Windows 8, you can most likely skip the XP installation steps above, of course.

Install Debian

  1. Download UNetbootin to the new Windows 8 machine. No need to install, it’s a standalone application.
  2. Use UNetbootin to create a bootable Debian installation flash drive. All the actual Debian files will be downloaded during the installation, so the flash drive can be small (I used an old 256 MB one). I went with the Debian Stable_Netinstall, worked well.
  3. Reboot the computer to start the Debian installer. If the entire disk was allocated to Windows during that installation (it would have been, unless you repartitioned it yourself) you need to make some space for Debian. The Debian installer allows you to do this in the partitioning section. Go to the partition that Windows is installed on, hit enter and you can edit the size of the partition. Apply.
  4. While still in the partitioner, move to the now free/unused space on the SSD, and use the assisted partitioner for all unused free space. Going with the recommended option (all data on same partition) is fine. You will then get /dev/sdb5 and /dev/sdb6 partitions for general use and swap, respectively.
    NOTE: When booting from the USB flash drive it gets the name /dev/sda. The SSD is /dev/sdb, with the Windows partition being called /dev/sdb1.
  5. The Debian installer can be a bit cryptic the first times you use it, but it’s not too bad. Going with the defaults is usually fine.
  6. One of the last steps is to install the GRUB boot loader. Now, this can be done different ways. The easiest is to just follow the suggestion to install GRUB to the Master Boot Record. This will overwrite Windows boot loader (which in Windows 8 is actually pretty nice, with graphical UI, mouse interface etc).
  7. When the Debian installer finish and the computer reboots, quickly remove the flash drive and if all is well GRUB should now kick in, showing Debian side by side with Windows 8.

If you want to use the Windows 8 boot loader, you need to reinstall it. I first thought I would do this, but changed my mind.. GRUB might not have the pretties UI around, but it works.

I think the last part of this article might be useful if you still want to switch back to using Windows 8 boot loader.

Closing thoughts

Now that XP is no longer anywhere on that SSD, it should be safe to switch the BIOS back to proper SATA mode. Windows 8 didn’t boot when I did that though… Not sure why. After switching back to the old legacy mode both Windows 8 and Debian boots fine, so I guess that decides it.

I did actually also do some initial work on the SSD, upgrading the firmware of it, as well as using the GParted Linux distro on a flash stick (once again using UNetbootin to create the flash disk) to create a FAT32 partition and align it as described in this post. No idea if that was really necessary..

Misc sources providing input for the above

http://www.howtogeek.com/99060/how-to-dual-boot-windows-8-and-linux-mint-on-the-same-pc/
http://unix.stackexchange.com/questions/76932/installing-debian-7-besides-windows-8
http://askubuntu.com/questions/217904/installed-ubuntu-my-windows8-not-booting/218006#218006

JBC CD-2BC soldering station unboxing

Got a new toy the other day…

After using the same ERSA MS 6000 soldering station for the past 20 (!) years or so, it was time to upgrade. Nothing wrong with the old one really, except that it was hard to get new tips and that heating it up took a minute or two.

Getting a Chinese rip-off from eBay would be easy, but if the next soldering station would also last 20 years, why not get something slightly better?

JBC has a good reputation and seemed to have good value for money. So – here are some pics from the unboxing. Enjoy!

Two dollar variable fan controller

Well – given current exchange rate, AU 2.59 = USD 2.33.. So it’s not quite a two dollar product, but pretty close. And “2.33 dollar fan controller” did not make for a nice subject line…

After the earlier post about variable 12V fan controllers, it might be worth looking at what is available on Ebay. Turns out you can get a variable controller delivered anywhere in the world for USD 2.33 – pretty amazing! It looks deceivingly like the Zalman Fan Mate 2 too:

Zalman Fan Mate 2 (left, USD 7) and eBay ditto (right, USD 2.3)
Zalman Fan Mate 2 (left, USD 7) and eBay ditto (right, USD 2.3)

The eBay controller only has one 3-pin male connector (where the fan connects), and then a soldered in wire with a 3-pin female connector, for attaching to the PC or other equipment.

The Zalman on the other hand has a 6-pin male connector on one end, a special Y-cable (it comes with the Fan Mate 2) is then needed to hook up the controller to fan and PC. Both variants of course work, the Zalman approach is maybe slightly better, as it allows the controller to be mounted closer to an inside corner, without the cables being in the way. Not a major difference though.

Looking inside the eBay controller, it is obviously different from the Zalman. For starters, it has a NEC B772 P PNP medium effect transistor in there, rather than a voltage regulator. I could not find a datasheet for that particular NEC device, but I am pretty sure it is more or less identical to ST’s 2SB772.

There is also a TL431 adjustable voltage regulator in there, together with a second SOT23 transistor market J6, it might be a S9014 NPN transistor (or equivalent).

So, in essence the eBay controller is also a linear regulator, but based off an adjustable regulator (rather than the fixed-voltage 7805 that the Zalman uses), with an extra power transistor to boost current. The extra transistor is needed, as the TL431 can only sink 100 mA on its own.

All good so far. But when reverse engineering the eBay controller, the schematic just doesn’t add up. Below is what the eBay controller looks like, with the above assumptions on components – and this is not a working circuit, as far as I can tell (or is it? Feel free to add your expertise in the comments!).

eBay variable fan controller - except that the circuit is a bit weird.. Need to re-check those PCB traces!
eBay variable fan controller – except that the circuit is a bit weird.. Need to re-check those PCB traces!

So…. either I made incorrect assumptions regarding what SMD components are used in the eBay controller, or I just didn’t check closely enough how the PCB traces were connected. Time to bring out the multimeter to check those traces – more to come on this topic.

Fritzing vs circuits.io vs Eagle – comparing schematics editors

During the recent work on the one dollar variable fan controller, I looked into options for documenting the work.

I have never really used CadSoft Eagle enough to get comfortable with it, and whenever I used it it seemed to be overkill for what I wanted to do. Still, it is usually still seen as the best software for this kind of work.

But maybe there are other options.. In particular I thought the more basic editors sounded promising – let’s give them a try. Disclaimer: Nothing near a full review was made of the different services. The verdicts below are instead based on 15-20 minutes use of each service, and no reading of any manuals or help pages.

Circuits.io

This would be the new kid on the block. Mix schematic editor with GitHub and you get something like Circuits.io. You can follow circuits created by other people, fork your own variants of other people’s circuits etc. Very nice concept, but it also seemed to have a lot of limitations..

circuits.io one dollar fancontroller
Circuits.io used to create a one dollar variable fan controller

For example, I failed mirroring the 7805 in the circuit to the right. Having the output to the left feels very awkward.. I am sure there are ways around it, but even though I really searched for it, I also failed to find a traditional 7805 symbol such as the one in the second image, and was left with the one used in the top schematic. Fail.

Traditional 7805 symbol
Traditional 7805 symbol

There for sure are nice things about circuits.io though. Having an entirely browser based editor is a very nice concept. It might be too early days for it now, but good things come to those who wait… I also liked the feature where you, given a PCB board design, can get files for 3D printing or milling a custom case for your board. Nice!

The fan controller project can be found at http://www.circuits.io/circuits/4841. Go fork it!

Fritzing

This is also a pretty new project, with a lot of promise. It is obviously geared towards hobbyists that might not have a ton of experience in electronics design, but it is still kind of nice.

One dollar variable fan controller, using Fritzing
One dollar variable fan controller, using Fritzing

With a slogan of “from prototype to product” it is clear that the Fritzing team is trying to cover it all. Not sure I would want to go this route with a full project though – I always get suspicious about software that offer a link to some third party service (in this case for manufacturing of PCBs). It probably works perfectly fine – I just feel left without the control I want to have.

Breadboard view in Fritzing
Breadboard view in Fritzing

The schematics editor is nice (better than circuits.io), and I even like the slightly silly feature where you can get a breadboard view of the circuit. Probably not a bit useful for an experienced electronics hacker, but still kind of cute.

The fan controller project can be found at http://fritzing.org/projects/one-dollar-variable-fan-regulator

Eagle

CadSoft Eagle is a professional schematics editor and PCB layout tool. The free version does have some limitations (PCB size and # layers, among others), but they are pretty generous and won’t cause any problems for most hobbyist projects.

The UI feels a bit dated, to be honest. But also quite efficient, given the vast number of components available. Seems lots of people also create their own Eagle libraries with various components, so there is a good chance you can find, download, install and use existing libraries. Otherwise it’s not too hard to create your own, half an hour of fiddling around with libraries left me with a working one. Nice!

Of the three tools Eagle is by far the best, even when considering the somewhat steep learning curve. Give it an hour and you will be able to create fairly complex circuits. PCB layout is still a bit of an art, no matter what product you use – you just have to learn as you go along, and from mistakes. Eagle does have some nice tools for eliminating the most obvious errors though – once again, nice.

All in all, going forward Eagle will (still) be the preferred solution around here.

One dollar variable fan controller

2013-08-09_22-06-40_copyWhile trying out various computer and network gear, I quite often find the fans too loud. They are of course there for a good reason, but experience tells that the device usually works just fine with less cooling. Best case one or more fans can be removed altogether, even though that is typically not recommended. They are of course put there for a good reason..

Anyway, I have repeatedly found myself looking for an easy solution to control the speed of regular 12V fans. Something that is just plug-and-play. Ideally also cheap or even free.

Going through a 7805 data sheet for other reasons, I suddenly realised that a 7805 set up in variable voltage configuration (figure 4 in the data sheet) should work great as a fan controller. These 12V fans usually run just fine down to 5-6 volts, but at lower rpms, and thus quieter. Just what was needed!

The circuit is quite basic:

7805 based variable fan controller
7805 based variable fan controller

The circuit is pretty clever – by shifting the ground to a higher level than the common ground/0V level, we get the voltage regulator to output between ca 6V and 10.5V. The component values were ones I had in my junk box, making a point of only using scavenged parts (don’t forget a heat sink for the 7805!) plus a little piece of strip board, the cost for me was actually zero. Nice!

A possible drawback of the design is the fact that a linear regulator like the 7805 will get rid of all (well… most anyway) excess energy as heat. A proper heat sink is thus definitely needed. An option would be to use some kind of low drop-out voltage controller (to get the upper limit closer to 12V), but it would have the same issue with heat dissipation. A better/easiesr option is probably to use one of the many PWM fan controller ICs available (here is Maxim’s list, there are plenty others too), it deals with at least some of the heat waste issues. You might be able to get some free samples too if you just want to play around with them. Most of them are not too expensive though.

All working well thus, and the story could have ended there.. However, a week or two later i was pulling apart an old PC when I found a couple of Zalman Fanmate 2 controllers… Too much of a coincidence not to see what made them tick.

Zalman Fan Mate 2, variable fan controller
Zalman Fan Mate 2, variable fan controller

After pulling one apart it turns out it is using exactly the same circuit as above! They did go a bit cheap and skipped the smoothing caps though, seems to work fine anyway – the fans won’t care much about some noise on their power line.

Also, the heat sink seems quite small and the controller is only specced to 6W, which is half of what the 7805 should be able to handle (it can handle 1A, so 1A*12V = 12W max power, with a proper heat sink).

Interestingly enough the Zalman controller costs ca USD 7 – not a huge amount of money, but one dollar to buy the components of your own (or even zero!) is a lot better..

Some additional shots of the Zalman controller:

QNAP TS-219 + Western Digital Green drives = FAIL!!

These days I am all in on the Intel Atom based Netgear NAS products, using a RN312. Very nice NAS, so far.

2013-08-15_13-06-12

The previous NAS in the server rack was a dual disk QNAP TS-219. Lower spec:ed with 512 MB RAM and an ARM based CPU. Still, it provided quite nice performance, and QNAP has been really good at releasing new firmware also for their older NAS versions (better than Netgear, actually, who won’t release their latest OS for the Ultra series, for example). 

Anyway, in preparation for selling the QNAP I figured I would put a couple of 1 TB Western Digital Green disks (that I wasn’t using) in it, upgrade to latest firmware, format the disks etc – everything to make it as nice as possible for potential buyers.

2013-08-15_13-08-53

After A LOT of trying, re-trying and trying again I gave up. It just didn’t work. The QNAP would recognise both disks, but performance was just terrible. Logging in via ssh and typing text worked – sometimes – but just as often it took 10-20 seconds between characters could be typed on the keyboard.

The web UI was equally unresponsive. When trying to combine the disks into a RAID 1 it just didn’t work. Total FAIL.

I guess I should have read the manual… On QNAP’s web site there is a compatibility list, with drives both suitable and NOT suitable for their NAS products. The list of unsuitable drives is not too long, but the Western Digital drives were on it. Come on… These drives are hugely common on the market.. why wouldn’t they be supported? What can be so strange about them?

Anyway, after replacing them with a couple of 250 GB Seagate Barracuda 7200.9 drive things were super smooth and the NAS was running like never before. All good in the end thus.

Lesson learned: Start looking for explanations online before spending too much time trying to solve things yourself..