CE's Blog

Many end-users are using CD-R or DVD-R media as a convenient storage for backup data. However the quality of writable media degrades over time; which inevitably leads to a loss of all or part of the stored data. In some cases, data loss can already occur within the first year after a media has been written. As a consequence, the data needs to be copied in regular intervals, before data loss happens.
Now the important point is how to determine the right time when a disc has to be copied. If copied too early, time and media are wasted. If copied too late, data loss has already occurred which might not be recoverable. Unlike a piece of printed paper, where the text on it is fading over time, the degradation of data on optical media is usually not linear and there are no clear signs that would signal if the media is about to fail or not.

There is an open source project called dvddisaster which has tackled this problem using an interesting approach: Before an ISO image is written on a media, it can be stuffed with extra error correction data that will be transparrently embedded along with the actual data. This gives gives extra redundancy to an extent that can be controlled by the user and depending on the free space remaining on the media.

While the idea of adding redundant error correction codes to important data is not new, the novelty lies in the concept of adding this information invisibly on a level below the visible file system. If any disk with error correction information is starting to deteriorate and some sectors become unreadable, we can still recover the real data that was stored in these sectors – provided that the redundant data is enough for recovery.
This brings the advantage that slight data loss is not critical, but can now be used as an indicator of aging media. With this approach one can actually wait with copying until some of the media’s sectors become illegible – wthout having to fear any loss of data.

dvddisaster is open source software, which makes it less likely that you will find a discontinued software if you need to recover a CD 10 years from now. As an added benefit, it is cross platform, so you should be able to use it from Windows and Linux.

Distances in Japan are huge, despite the excellent Shinkansen rail network. In case you are planning to visit Hokkaido from the Tokyo bay area and do not want to afford a ride on the northbound Shinkansen to Akita or Aomori, there is an inexpensive solution for a five day Hokkaido trip.

I am talking about the time limited 北海道＆東日本パス, which is valid from Novermber 30, 2007 until January 20, 2008. It is a special 5-day pass for Hokkaido and northern Japan and sells for only 10,000 円. With this pass you can take all slower JR trains between Itō, Shizuoka, and Wakkanai on Hokkaido.

If you want to use this ticket for long distance travel, the main problem is that the trains are pretty slow, and you have to change trains a lot. I went to Tokyo main station and asked the information desk to print out a travel plan for going to Sapporo within a single day. The answer was that it is not possible with this train pass. Since I insisted to find a solution, the guy behind the desk started to search, then he started to sweat, and after some time he finally called his superviser. For their own surprise, they were able to find a solution. 15 minutes later I walked out with a long list of trains and transfer times, with the shortest time being only 2 minutes to run from one train to the other.

So the next day my journey started in the commuter train at 7 am in Ueno station. After changing trains ten(!) times, I got to Morioka at around 5 pm. Lots of snow everywhere, and time for a dinner break.
Entered the ‘Hamanasu’ night train at 22:15 bound for Hokkaido. Althought this is a fast train, the pass is also valid!

Finally got to Sapporo at 7 am the next morning! Hopped on the next train to Asahikawa, and once there on the “Ochotsk” train to Abashiri. Got there at around noon, perfect!
One more thing to mention: The JR pass will also give you a huge discount in most youth hostels on Hokkaido.

So by finding a smart train connection and a bit of luck you can travel Hokkaido from Tokyo and back within 5 days.

On the way back from Sapporo, you can board the ‘Hamanasu’ night train at 21:30 to Aomori, arriving at 6 am. It is still a long ride, and if you are unlucky (like me this time) you won’t be in Tokyo before 1 am. It is possible though to make the whole trip back in a day, so just go for it!

Here is a scan of the Hokkaido Pass flyer: