Category Archives: Linux

Ultra compact PC..

Odroid has released a new set of Ultra compact ARM based boards. Smaller Odroid-U2 is only 48x52mm in size (less than credit card), its big brother being 90x94mm. Both devices have quad core ARM processor (Samsung Enyxos 4412), with 2 gigs of RAM, MALI-400 quad core GPU, 10/100 Mbps LAN, USB 2.0 ports, HDMI port and MicroSD/eMMC sockets.

These computers are able to run Android or Linux based OS (E.g. Ubuntu) and there is already few videos in the Youtube where you can see these tiny computers in action.

See more information from the manufacturer’s site: ODROID – product catalog

And check the great videos from: ODROID videos on Youtube

Linux tweaks..

Data scrubbing may render your RAID array unsable silently. To prevent that it is recommended that data concistency and bad block check is run regularly on RAID. This can be done by appending word check into /sys/block/mdX/md/sync_action, where X is your RAID device number.

echo check >> /sys/block/mdX/md/sync_action

I was pretty shocked when I noticed that the check was going to take 15000 minutes which equals to 250 hours. I planned to run this check bi-weekly and with these numbers my RAID would have been busy checking bad blocks 75% of time. It seemed like something was not right in the RAID. Luckily there is lot of information about Linux software RAID and their tweaking in Internet. Couple tiny changes into /etc/rc.local fixed the issue and now we are talking about magnitude of 360 minutes instead of 15000. Here are the fixes I made.

# This one alone helped the most
echo 4096 > /sys/block/md0/md/stripe_cache_size
# These two rows help with the read speed
blockdev –setra 4096 /dev/sd[a-d]
blockdev –setra 16384 /dev/md0