Migrate from RAID 6 to RAID 5 with mdadm


lian-li-qo08bI have been using a quite secure setup for the last couples of years with a 4 drive RAID 6 setup. This setup can tolerate two disk failures without any data loss. Recently though, I have been getting close to the edge of the filesystem and could use some extra space and since I have both monthly backup to an external hard drive and nightly offsite backup I am actually not very afraid of a data loss on a RAID 5 setup. So I have planned to change my 4 disk RAID 6 to a 4 disk RAID 5 without any spares.

A word of caution: Please do not do any of the actions below before a backup has been made.

Continue reading Migrate from RAID 6 to RAID 5 with mdadm

Completely silent and powerful workstation, spring 2013

Someone in my close family needed a update for a workstation primarily used for emailing, browsing, audio and light video editing. The computer was never used for any 3D demanding games, so no separate GPU was needed, provided that I could find a CPU with a on-die GPU. Furthermore a recently bought NAS took care of all the large files, so the objectives for the build was to create a silent, very fast booting computer that could also handle heavier problems as audio and video editing.

The following build is completely silent. The case has built-in heatpipes that cools the CPU, the PSU is also fanless and the SSD doesn’t make a sound. Still the SSD is blazing fast, the i5-3570K CPU is very capable and the on-die HD4000 GPU is more than enough for the workstation.


Mid January 2013 in Denmark this totaled, with delivery, to 6711 DKK (1210 USD).

  • CPU: Core i5 3570K, 6 MB
  • MB: Gigabyte GA-Z77N-WIFI, mini-ITX
  • GPU: Intel HD 4000 built-in on the i5-3570K
  • CASE: Streacom FC8B EVO Black, Mini ITX, Passive Heatpipe CPU Cooling
  • PSU: Streacom NANO150 PSU Adapter, Passive
  • SSD: Samsung SSD 840 Series 250GB, 540/250MB/s
  • RAM: Corsair Vengeance 2 x 4 GB, low-profile, PC3-12800, 9-9-9-24
  • DVD: Sony DVD Writer, AD-7640S, slimline
  • Cables 1: SATA adapter for SATA slimline DVD drive, 6+7 pin, slim SATA – 4-pin power + 7pin SATA
  • Cables 2: Streacom SC30 USB3.0 Internal Cable

Continue reading Completely silent and powerful workstation, spring 2013

YABI – Yet Another Boids Implementation (simulation of flocking animals)

Just before I started my paternity leave I saw a documentary about flocking animals and how these can be modeled in computer simulation. I found it very exciting and eagerly thought I could implement a simulation in a days work. I, however, quite underestimated the free time available while on paternity leave and the project extended in to many pieces spread over a few weeks. First a little teaser from the animation I made using python and Matplotlib, where the Boids (birds, fish or flying sheep ..) are in blue and predators are in red:

Continue reading YABI – Yet Another Boids Implementation (simulation of flocking animals)

Photography: Channel mixer RGB values equivalent to traditional B&W film

I have a Nikon D90 DLSR and and from time to time I want to convert color photographs these into B&W photos. I use the open-source and completely free GIMP to edit the pictures and do B&W conversion.

Using the built-in grey scale conversion often doesn’t come out to nicely, so I was wondering how to emulated the classic B&W films using the channel mixer in GIMP. I turns out that Petteri Sulonen on his blog www.prime-junta.net had done just that. On the left I am showing the Channel Mixer window in Gimp to converting a color photography using the Ilford XP2 Super channel settings. Below is list of his findings (I have done this mainly to have a online copy in case his blog goes offline).

My only small contribution is a ZIP file with all the profiles saved as GIMP channel mixer settings files, so the profiles can easily be loadd: GIMP-BW-film-Channel-Mixer.zip 6KB.

Film Name Red Green Blue
Agfa 200x 18 41 41
Agfapan 25 25 39 36
Agfapan 100 21 40 39
Agfapan 400 20 41 39
Ilford Delta 100 21 42 39
Ilford Delta 400 22 42 37
Ilford Delta 400pro 31 36 33
Ilford FP4 28 41 31
Ilford HP5 23 37 40
Ilford SFX 33 36 31
Ilford XP2 Super 21 42 37
Kodak Tmax 100 24 37 39
Kodak Tmax 400 27 36 37
Kodak Tri-X 25 35 40

Silent gaming PC build, September 2012


My old workstation and gaming PC is now 6 years old and it is beginning to feel slow. A few weeks back I set out to build the replacement and my main objective was that it should be silent, but powerful, so I have search the net for reviews and recommendations and the following is the items I decided to buy:

  • CPU: Core i5 3570K, 6 MB
  • MB: ASRock Z77 Extreme4
  • CPU-cooler: Noctua NH-C14
  • GPU: Sapphire RADEON HD 7950 OC (3 GB)
  • CASE: Fractal Design Define R4
  • PSU: Sea Sonic M12II-520Bronze
  • SSD: Samsung 830 Series MZ-7PC128B, 128 GB
  • RAM: Corsair Vengeance 2 x 4 GB, low-profile, PC3-12800, 9-9-9-24
  • DVD: Samsung SH-222BB, DVD-burner

On the day it was bought (21-sep-2012) this totaled, with delivery, to 8430 DKK (1470 USD).

Update – overclocked CPU, underclocked fans, decided against 7950

I have now received all the parts, put them together and I am happy to report that it is a very silent build. 🙂 The only change I made in the last second was to drop the 7950 GPU as the rumors of the 8850 are just starting to emerge and I can cope with my 5850 until then. If anybody is using this article mind also that the Samsung 840 SSD has just been launched and it should be very impressive. I couldn’t wait for the 840 to come to Denmark, so I am perfectly happy with my 830.

Additional notes: The Noctua C12P cooler comes with two extra cables to reduce voltage on the fans – Low-Noise Adaptor (L.N.A.) and a Ultra-Low-Noise Adaptor (U.L.N.A.). These adaptors reduce the original fan speed from 1200 RPM to 900 and 750 respectively. I am using the 900 RPM L.N.A. version it is hardly audible and still coolers sufficiently. Another great thing is that the Fractal Design R4 Case comes with built in adaptors for the case-fans which be control on front, see image. I have found that the lowest setting (5V) is sufficient for me and it is very silent. To put in into perspective I have a moderate overclock from 3,4 to 4,2 GHz while having underclock most of the fans and the system is both stable and not be any means too hot.

Core i5 3570K, 6 MB

The first thing I decided to buy was the i5-3570K. It seems to be the new king of mid range with a great performance/cost ratio. It has a great potential for overclocking and is a significant step upward from my old Intel E6600 CPU.

Much like the Sandy Bridge i5-2500K processor was the best value in terms of price and performance for the 2nd generation Intel Core processors, the Ivy Bridge i5-3570K will surely be a popular processor among enthusiasts on a budget. The i5-3570K does not have the i7-3770K’s Hyperthreading capability but is more than powerful enough for most tasks even at stock clocks. Since it is a K processor, the i5-3570K can easily be performance tuned to reach the i7-3770K’s stock performance and is as equally impressive in this regard as the i5 2500K before it.

Review – hitechlegion.com (quoted)
Review – hexus.net
Review – bit-tech.net
Continue reading Silent gaming PC build, September 2012

Computers and physics