Month: November 2008

I have written some posts on the issues I have had over the past week with my Dlink DNS-323 NAS. As I wrote yesterday I configured the system to use JBOD to combine the size of the two Samsung 250GB disks and then fill the entire array with data to verify that I would be able to recover the files from one of the disks if the other failed.

The findings are interesting. Please read on.

Once both disks were completely full I powered down the DNS-323 and connected one disk at a time to a computer running Ubuntu 8.04, using a SATA-to-USB adapter.

The leftmost disk showed the following partitions:

However, the partition /dev/sdb2 would not be mounted. The error in the log was “VFS: Can’t find an ext2 filesystem on dev sdb2”.

I then switched to the other disk (the one on the right). The partition table looked identical but this time I could actually mount the disk – but whenever I ran ‘ls’ I got a lot of errors saying “cannot access test/D0000220: Input/output error”. The error was caused by files that were on the other disk but were referenced by the file allocation table on this disk. The files that were on this disk were accessible, however.

I then studied what data had been saved on which disk and visualised it. In the image below, each pixel represents two files, each 1MB each in size. The first saved file is the one in the top left and it then goes across and down. Red pixels were saved to the left disk whereas blue pixels were saved on the disk on the right. The original image was 1000 pixels wide, I just shrunk it horizontally to be able to fit within the boundaries of this blog.

The fact that it seems very difficult to recover files on one of the disks means that I will probably stay clear of both JBOD and RAID for my DNS-323. Too bad.

This is a continuation of a previous post.

OK, the idea wasn’t exactly brilliant. The script worked fine but completely filling the disks (totally 500GB) from another computer was going to take up towards 40 hours and I am a little impatient. The bottleneck with the DNS-323 is as usual the network connection. So instead, I though about running the script on the DNS-323 itself – which should be very much quicker. But to do that I needed to install a fun_plug to be able to log on and run some software on it.

I had done some small tests with fun_plugs when I first got the DNS-323 but I haven’t checked how much could be done and I was pleasantly surprised. This is a step-by-step description on how to install Fonz fun_plug (FFP) and make it accessible through SSH.

1. Download fun_plug and fun_plug.tgz from this web site
2. Copy the files to the Volume_1 folder on the DNS-323
3. Make sure that the fun_plug file is executable
4. Restart the DNS-323, then telnet to get shell access
5. Install all packages as described in the readme for FFP

cd /mnt/HD_a2
rsync -av inreto.de::dns323/fun-plug/0.5/packages .
cd packages
funpkg -i *.tgz


6. Enable the root password and set a password as well as the shell for root by issuing the following commands

pwconv
passwd
usermod -s /ffp/bin/sh root


7. Verify that you can log on as root

login


8. If the login worked, then store the password to flash memory by running

store-passwd.sh


9. Start the ssh server (which will take a while since it has to create keys), then try to log on from another computer

cd /ffp/start
sh sshd.sh start


10. If that worked it is time to turn off the telnet server and to enable the ssh server instead

chmod a-x telnetd.sh
chmod a+x sshd.sh


I am now running the script on the DNS-323 and it is about 7 times quicker than running it via Samba.

More to follow…

This is a continuation of a previous post.

With all my important data on another disk it was finally time to upgrade the DNS-323 to the newest firmware and to reformat the disks. This also brought up the question whether I should use JBOD or separate disks. After searching on the Internet, there seems to be a lack of evidence of just how the DNS-323 handles disks in a JBOD array. And so I wondered if maybe I should test and document it.

To do that I wrote the following little Bash script and run against the JBOD array from another computer. The script creates numbered files, each with a size of 1MB. 1000 such files are placed in each directory. The plan was to fill the entire disk and then take out the disks to study and see what the DNS-323 had stored on each disk and to verify that the content on a disk would in fact be accessible if the other disk broke down.

#!/bin/bash
 
TARGET=/mnt/nas
FOLDERS=500
FILES_PER_FOLDER=1000
BLOCKS_PER_FILE=2000
 
if [ ! -d $TARGET ]; then
  echo "Target folder does not exist"; exit
fi
 
for d in `seq 1 $FOLDERS`; do
  dirname=`printf 'D%07d' $d`
  echo "Creating folder: $dirname"
  mkdir $TARGET/$dirname
 
  echo " Creating file: F0000001"
  dd if=/dev/zero of=$TARGET/$dirname/F0000001 count=$BLOCKS_PER_FILE
  for f in `seq 2 $FILES_PER_FOLDER`; do
    filename=`printf 'F%07d' $f`
    echo " Copying file: $filename"
    cp $TARGET/$dirname/F0000001 $TARGET/$dirname/$filename
  done
 
done


Please check back for the result of these tests.