Masterzen’s Blog

The curse of bad blocks (is no more)

2 minute read

If you like me are struggling with old disks (in my case SCSI 10k RPM Ultra Wide 2 HP disks) that exhibits bad blocks, here is a short survival howto.

Those disks are placed in a refurbished HP Network RS/12 I use as a spool area for Bacula backups of our Apple XServe RAID which is used by Days of Wonder graphic Studio (and those guys knows how to produce huge files, trust me).

Since a couple of days, one of the disk exhibits read errors on some sectors (did I say they are old), so waiting to get replaced by other (old) disks, I had to find a way to have it working.

Of course the SCSI utility in the Adaptec SCSI card has a remapping tool, but you have to reboot the server and have it offline during the verify, which can take a long time, so that wasn’t an option.

I then learnt about sg3_utils (sg3-utils for the debian package) thanks to the very good page of smartmontools bad blocks handling.

This set of tools directly address SCSI disks through mode page, to instruct the disk to do some things. What’s interesting is that it comes with two commands of great use (there might be more of course):

• sg_verify: to check for the health of a sector
• sg_reassign: to remap a dead sector to one from the good sector list

Here is the use case:

backup:~# dd if=/dev/sda iflag=direct of=/dev/zero skip=1915 bs=1M
dd: reading `/dev/sda': Input/output error
12+0 records in
12+0 records out
12582912 bytes (13 MB) copied, 1.41468 seconds, 8.9 MB/s

Something is wrong, we only read 13MB instead of the whole disk. Let’s have look to the kernel log:

backup:~# dmesg | tail
[331709.192108] sd 0:0:0:0: [sda] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE,SUGGEST_OK
[331709.192108] sd 0:0:0:0: [sda] Sense Key : Medium Error [current]
[331709.192108] Info fld=0x3c3bb1
[331709.192108] sd 0:0:0:0: [sda] Add. Sense: Read retries exhausted
[331709.192108] end_request: I/O error, dev sda, sector 3947441

Indeed /dev/sda has a failed sector (at lba 3947441).

Let’s confirm it:

backup:~# sg_verify --lba=3947441 /dev/sdaverify
 (10):  Fixed format, current;  
 Sense key: Medium Error Additional sense: Read retries exhausted  
 Info fld=0x3c3bb1 [3947441]  
 Actual retry count: 0x003f
 medium or hardware error, reported lba=0x3c3bb1

Check the defect list:

sg_reassign --grown /dev/sda
>> Elements in grown defect list: 0

And tell the disk firmware to reassign the sector

backup:~# sg_reassign --address=3947441 /dev/sda

Now verify that it was remapped:

backup:~# sg_reassign --grown /dev/sda
>> Elements in grown defect list: 1

Do we have a working sector?

backup:~# dd if=/dev/sda iflag=direct of=/dev/null bs=512 count=1 skip=3947441
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.00780813 seconds, 65.6 kB/s

The sector could be read! The disk is now safe.

Of course, this tutorial might not work for every disks: PATA and SATA disks don’t respond to SCSI commands. For those disks, you have to write on the failed sector with dd and the disk firmware should automatically remap the sector. This can be proved by looking at the **Reallocated_Sector_Ct **output of smartctl -a.

Good luck :-)

No more slides, welcome to our Digital Overlords

4 minute read

If you had a look to my About Me page, you know that one of my hobby is photography.

Until a couple of weeks ago, I was still doing analog photography with a Nikon F100 and the fabulous Fuji slide film: PROVIA 400X. This slide film is the best I could ever use in my whole amateur photographic life, it has almost no noticable grain for a 400 ISO slide film and a wonderful respect of color.

But enough of this, on January 5th 2009, I left the analog world for the digital world with the help of a brand new Digital Reflex camera, the Nikon D700:

Why this camera? The only reason I came for this one is because it’s the first full frame Nikon digital camera. I didn’t want to bother with DX camera as I have 5 Nikon lenses (although compatible I’m most familiar with them on 24x36 ratio).

Let me first say that Digital photography is a whole lot different than analog photography: I now have the freedom to take hundreds of pictures of the same subject varying, bracketing, and tuning settings. I never did that with slide film (especially because of the price of said films and process). That changes everything of course. That and the ability to see the image after you took it. With slide film on a tight budget like I was, you have to be sure you’re doing the right picture. I can’t count the number of time I thought I could have done better on some pictures I took.

Other than that, the Nikon D700 **looks exactly like all my old analog Nikon cameras (from the F3 to the F100 passing by the F801) and I could use it almost without reading the manual: buttons didn’t change function or place. The D700 frame is nicely built with its **Rugged magnesium-alloy construction with dust and moisture protection, like the F100. What is also noticeable beside the FX sensor and its very large range of sensibility (up to 6400 without too much noise), is the large and bright LCD screen (which allows LiveView, a mode where you shoot your photo through the LCD and not the viewfinder).

And the speed. My first concern about digital photography was the speed to take a picture. Back a few years ago when everybody was purchasing Canon 1D, I thought it wasn’t possible to live with a 250ms delay between when you press the button and when the picture is taken. Now, this isn’t an issue anymore at least on the D700 since the delay is almost not noticeable.

As I don’t really have lots of spare time (contributing to Puppet takes time) and the weather was not as nice as I wanted it to be, so I only could do two sessions of photography in January.

The first one was in Parc Javel André-Citroen after it snowed. I was trying to understand the basic working of the camera, and see what I could get with it. I wasn’t disappointed at all: the piqué of the pictures is excellent. I should say that I combined the camera to a fabulous lens: the Nikkor AF-S 24-70 2.8G, which despites its weight is the most wonderful lens I had. Way better than my father Leica R5 lens…

Here is a sample of this session:

You can see the other shots in the Testing D700 gallery.

Then yesterday there was the Chinese New Year parade in Paris, in the 3rd and 4th arrondissement (which is since about 10 years, a place were there are lots of Chinese import/export shops). I’m usually not good at live report as I usually take my time to shot (did I say how I want each parameter to be fine-tuned and set as I want, especially depth of field?), so that was the perfect test for the autofocus (which I usually don’t use) and overall camera speed. And the camera passed this exam with success (or is it the photographer?).

Here is a few pictures from the session:

And if you want to see them all, see my Chinese New Year Smugmug Gallery.

What was frustrating with slide films was the efforts needed to digitize them and bring them online. Even though I had a Minolta Dual Scan IV slides scanner (of moderate quality), the powerful Vuescan scanner software, and some calibrated profiles for the Provia, the colors and contrast of the digitized slides were not satisfactory. And did I say it was time consuming? And removing dusts and scratches was also more than time consuming.

With a fully digital system, it is even simpler and fast to send your pictures online for broad view. In my case I chose Smugmug, mainly because the service seemed powerful, not expensive, but also because I’m reading Don MacAskill’s blog which contains lots of valuable information about MySQL, and/or server hardware.

To be noted also, that Nikon sells a really good picture enhancement software called Capture NX2. This software contains some really good tool (like the brush editing tool). I never used Adobe Lightroom nor Apple Aperture, and didn’t find yet an Open Source alternative, so I don’t really have comparison points. You can have look the Nikon screencast to understand why I think there are killer tools in Capture NX2.

To summarize, I think I did the right choice with this camera, and I do expect to post more pictures to my galleries (and you’ll see them in my Photostream).

Small World contest!

2 minute read

You certainly know that I work for the boardgame publisher Days of Wonder, and we announced a couple of days ago our new boardgame Small World:

What’s cool, is that we also launched a special contest in partnership with BoardGame Geek.

In Small World, you control several typical med-fan races (Elves, Amazons, Trolls…) combined with special abilities, who use their troops to occupy territory and conquer adjacent lands in order to push the other races off the face of the earth in the hope that they will rise to the top of this brutal land grab!In this contest, you have a single chance to vote for the character you think deserves to be the top race (or at least the one you believe other voters will pick as the most popular). In addition to voting for your favorite, you will also make two more selections to choose the races you predict will end up 2nd and 3rd most popular.

Participants who vote for the race that rises to the top and has the MOST top race votes when the contest ends will be the proud recipient of a Small World Bumper Sticker/Decal featuring the winning race.

Even better, if in addition to picking the winning race, you also are one of the first 10 participants to correctly predict which races end up as the #2 and #3 races (i.e. the 2nd and 3rd race to collect the most votes from contestants as their top pick), you will also win a free copy of Small World!Here’s the kicker (and what makes the voting dynamics really interesting)…

The current vote totals are visible in real-time to other entrants, so you can see how each race stands before you vote. The longer you wait to vote, the more likely you are to correctly guess which Race might rise to the top (and to the all important #2 and # 3 slots).

But if you wait too long, the more likely you are to lose out on the chance to win a copy of Small World since other participants will likely have made the same “correct” votes earlier.
Thus it may be a good strategy to vote early and then lobby, cajole (and bribe?!) all of your friends to come vote for the same races you voted for, in the hope that they can help your picks rise to the top!

Here are the current top races results:

Do not forget to enter your vote for: Small World - Only the Fittest Will Survive - Contest