Nov 7, 2011

iSCSI and LVM: Boot problem

Both LVM and iSCSI are powerful and reliable. But there is an issue with the combination of both that made me fell completely lost more than once.

The Scenario:
iSCSI target / server is a Linux Box with LVM features
iSCSI target / server exports disk, partition or LVM LV
iSCSI initiator / client uses the exported volume as LVM PV
All works perfectly until rebooting the iSCSI target / server

The symptom:
After rebooting the iSCSI target / server, it becomes impossible for the initiator / client use the exported volume as if it were deleted. The iSCSI target / server service itself is working properly but the exported volume is not.

The cause:
During the boot of the iSCSI target / server, its LVM liked the new found PVs / VGs / LVs. The iSCSI target / server has no idea about those new found are not for the local machine and it "locks" the VGs and LVs for local use. When iSCSI exports the LV, it will contain locked LVM volumes. This is why it becomes impossible to use it on the iSCSI initiator / client.

The solution:
It is very easy. Edit /etc/lvm/lvm.conf and use "filters" to tell LVM what is not for local use. My filter is configured as:

filter = [ "a/sda/", "r/.*/" ]

For testing, just type pvscan after editing the file to see if the filter worked as expected. If so, just reboot and it will work.

Please note that using sda on the filter is not the safest solution as it is not impossible that sda becomes sdb for example. It will be safer to use UUIDs of something else.

Nov 3, 2011

Acer Iconia Tab W501P Review II

Fedora 16 Beta

Feroda 16 Beta runs on the W501P without any major concern. The only issue I found is the Gnome onscreen keyboard that does not work well. Despite the onscreen keyboard, I did not found any serious issue when using Fedora on Iconia Tab W501P.

I did no testing with ATI proprietary drivers on Fedora.

Ubuntu 11.10

Ubuntu 11.10 also runs on the W501P but there are some details:
1 - When I allowed the installer to download updates during installation, the X did not work very well after first boot. So I installed it again and it is working pretty well without allowing the packages to be updated. I'll wait untill ATI driver supports the C-60 GPU until allowing updates.

2 - The ATI proprietary driver does NOT work with C-60 GPU. I've tried Ubuntu's two packages, "AMD Catalyst™ 11.9 Proprietary Linux x86 Display Driver", and "AMD Catalyst™ 11.10 Proprietary Linux x86 Display Driver". When using Ubuntu's package, an stamp with AMD logo appears on the right bottom corner saying: "Unsupported Hardware". I would not recommend to try those drivers with Ubuntu 11.10. It may be necessary to re-install your Ubuntu.

After learning about updates and ATI proprietary driver, I'm happy with Ubuntu on W501p. I'm curious about the performance gain by using the proprietary graphics driver. Will it be possible to play HD flash movies on full screen?

The battery

I was curious about the sleep state power consumption. I've charged the battery, and asked Ubuntu to sleep the tablet. I removed the charged cord and waited exactly 12 hours. How many % of the battery power were consumed in 12 hours?

The result is that after 12 hours of sleep state the battery charge was informed to be 92% by Ubuntu. 8% every 12 hours means 16% every 24 hours. Looks like that the Iconia Tab W501P can stay sleeping for more than 6 days. This is good!

Not tested yet battery life for usage. I think that this will be improved when the proprietary graphics driver is available.


Battery charge after 12 hours of sleeping

Nov 2, 2011

Recording from webcam, saving to file, displaying locally, using VLC, under Linux

# Change /dev/video1 to your webcam device name
# Change plughw:1,0 to your audio capture device. (Check /proc/asound/devices)
# Change 1920 to the correct width of your webcam ( Check Cheese preferences )
# Change 1080 to the correct height of your webcam ( Check Cheese preferences )

$ vlc v4l2:///dev/video1 :input-slave=alsa://plughw:1,0 :v4l2-standard=0 :v4l2-aspect-ratio=16\:9 :v4l2-width=1920 :v4l2-height=1080 :v4l2-fps=30 :sout="#transcode{vcodec=mp4v,vb=5000,scale=1,fps=30,acodec=mpga,ab=128,channels=1,samplerate=44100}:duplicate{dst=std{access=file,mux=ts,dst=/tmp/video-output.mpg},dst=display}"