Linux - 6

The short version is: it does not work.

Having a SSD is feasible in the long run only if there is possibility of operating system informing the drive that an entire drive block (typically 16 KiB) can be erased. openSUSE wiki has following quote in it: "There are three terms often used to interchangeably describe this same basic functionality: Discard, UNMAP, and TRIM." This discard is possible only when there are no operating system sectors (typically 512 bytes) in the drive block.

Here is what I tried to do: I installed two Intel® Solid-State Drive 520 Series drives into my server and tried to see if RedHat-based CentOS 6.4 has enough backported bits & pieces to support RAID-1 /w TRIM.

The drives are fine and kernel TRIM-support is there:

hdparm -I /dev/sda | fgrep -i trim
           *    Data Set Management TRIM supported
           *    Deterministic read after TRIM

My initial attempt had GPT-partition table with a single RAID-partition on it. The command I used is:

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1

I created EXT-4 on top of md0:

mkfs.ext4 /dev/md0

and mounted it:

mount /dev/md0 /mnt/tmp/ -o discard,noatime,nodiratime

The discard-support is in the kernel ok:

mount | fgrep md0
/dev/md0 on /mnt/tmp type ext4 (rw,noatime,nodiratime,discard)

The next thing I tried to do is confirm if TRIM does work either automatically or as a batch job. I followed instructions from this blog entry and tried to run hdparm --fibmap on a newly created file. It failed with a segfault. Apparently that is a known issue, so I ended up packaging the latest version myself. My own RPM-package is available at http://opensource.hqcodeshop.com/CentOS/6%20x86_64/hdparm-9.43-1.el6.x86_64.rpm.

With latest hdparm 9.43 I could verify that FIEMAP (file extent map)  ioctl() does not return correct results on a soft-RAID-1 device. The LBA-sector given by hdparm does not seem to contain the file's data.

My next attempt was to tear down the existing md0 and re-build it using entire drive as RAID-device.

mdadm --stop /dev/md0
mdadm --zero-superblock /dev/sda1
mdadm --zero-superblock /dev/sdb1
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda /dev/sdb
mkfs.ext4 /dev/md0
mount /dev/md0 /mnt/tmp/ -o discard,noatime,nodiratime

I ran the same test, but this time hdparm --fibmap informed it failed to determine the drive geometry correctly. A short peek into the source code revealed that current version of hdparm works only with partitions. It tries to load the RAID-partition start LBA even if it is not located on a partition. I made a quick fix for that, it turned out that /sys/block/md0/md/rd0/block has DEVTYPE=disk or DEVTYPE=partition to indicate the base drive type.

Nevertheless, it did not help. fibmap does not return the correct LBA-sector. I loaded a Bash-script to do the manual TRIMming of a SSD-RAID-1, but it only confirmed what I already knew. The LBA-mapping does not work enough to see if discard works or not.

Currently I don't have anything on my RAID-1, I'll have to see if it is possible to get the discard working somehow. A newer Linux might do the trick.

Couple of weeks ago openSUSE-project released their latest desktop-Linux. That is the distro The Man himself, Linus Torvalds had a dispute about security policy of needing a root access to add a new wireless network. He actually said that openSUSE-people are morons. A year ago, they were very defensive and insisted that Mr. Man had it wrong. In reality: no other operating system requires demi-god permissions to do such a trivial task. In 12.3 the morons finally got it, connecting to a new wireless LAN does not require any special permissions.

My hardware for running a desktop-Linux is a very old Apple MacBook. The Mac OS X system info says, that this is a 1,1 hardware, making it pretty much one of the first ever Intel Macs there exists. It has two gigs of RAM and enough hard disk to run pretty much any modern disto. Being a Mac, it also has enough Intel chips in it to fulfill any requirements that modern distros have for 2D or 3D graphics, sound or display. It definitely lacks the I/O or CPU power that any not-6-years-old laptop might have, but it is very suitable for running a desktop-Linux. Mr. Torvalds prefers Apple Airs, but I didn't want to spend that much money on an used computer.

openSUSE install just keeps on improving. I always back up the old computer and do a fresh install, I sure haven't met a working operating system upgrade ever. During installation, all the settings are there if you need the, but the defaults are very good making the entire process flow smoothly. This time there was a glitch when the Atheros WLAN-chip was not auto-detected during install. I had to manually go configure network devices and add a wireless device. At that point the ath5k driver was detected and I got the box connected to The Net for the rest of the install. No other special things there.

After install the first thing I got was the pommed-package. It makes the Apple-keys work in Linux and is definitely needed. My keyboard layout is Finnish, so I also had to compile keyfuzz to get rid of those useless Apple-keys which are called Meta-keys in Linux. I need my alts, and do the following mappings:

 # Map Alt to Meta
458978 125
# Map Meta to Alt
458979 56
# Map Right Meta to Right Alt
458983 100

The final thing to do is to get the iSight-camera working. All it requires is the Apple-copyrighted firmware and it is ready to go. What I did, was to restore my previous file from a backup, but if you need to get one for yourself, there is ift-package or iSight Firmware Tools. With that you can extract the needed bits from Mac OS X device driver and place the resulting file into your Linux. There already is a Linux kernel-module isight_firmware waiting for the file to appear. As a result a brand new Video4Linux-device should appear and you can test it with MPlayer (that breaks couple of dozen copyrights and you need to get from The Net):

mplayer tv:// -tv driver=v4l2:width=320:height=240:device=/dev/video0 -fps 30

The 12.3 runs clearly much faster than 12.2. I have all the KDE4-desktop effects enabled and 12.2 really couldn't manage the 3D-graphics. 12.3 seems to be able to get more juice out of the Intel's 945 GPU. With all the modern software and latest Linux kernel the open-source -guys are finally getting there (with support from Novell, of course). This is actually a very usable desktop for a geek like me.

openSUSE 12.3 get's my seal-of-approval with a bonus thumbs up.

I bumped into couple of issues earlier. Article about missing Integration Services and Networking Status: degraded.

RedHat managed to package the Integration Service drivers into RHEL 6.4 which essentially is the base of CentOS 6.4. So, from now on the much required drivers are bundled in the installation source.

There are no major changes in the drivers, though. Network status is still degraded and a hint of upgrading the drivers is there. It seems to be a mystery to everybody how to do the upgrade.

The list of integration services is unchanged:

• Operating system shutdown
• Time synchronization
• Data Exchange
• Heartbeat
• Backup (volume snapshot)

This article in Microsoft's social network describes the changes. Looks like Dynamic Memory (ballooning) is the only new feature. That wasn't even in the RHEL 6.4 beta, but they pushed it into final release.

Earlier I wrote about running CentOS 6.3 with Windows 8 Hyper-V.

One day I realized that the status of my network says: Degraded (Integration Services upgrade required). Well... I dunno what that means. Everything seems to work, but if there are any issues I'm not noticing them.

According this conversation at Microsoft's social network, somebody else is having this issue too. They are not noticing anything wrong either. Except the fact that status is degraded. I did try fiddling around with virtual network settings, but no avail.

I guess it is fully working after all.

Windows 8 Pro comes with Microsoft's Hyper-V virtualization platform. If you have new and beefy PC, it is likely that the CPU supports Hyper-V (Celeron owners, don't bother). Everybody needs couple of Linuxes running inside your Windows, right? At least I do.

Getting the newly installed CentOS 6.3 to support networking is a bitch. After the CentOS installation finishes you're left on a virtual console screen with little possibilities of getting to outside world from your sandbox. The Wikipedia article about the subject reveals, that Microsoft had to submit their code into Linux kernel to comply with GPL license requirements. But still, CentOS 6.3 has kernel 2.6.32, but the much needed Hyper-V kernel modules are not available. Darn!

It took me an hour of Googling around, before I ended on Microsoft web page titled Linux Integration Services Version 3.4 for Hyper-V. I got the .ISO image, mounted it into my virtual Linux and run the install script. Yesh! The script managed to get my NIC to appear as eth0. After that it was just a breeze to get it configured with DHCP-client. It's a pity that nobody clearly documents this part of the installation process. People could save hours of work if somebody said to go get them.

Apparently new Linux distros come with Hyper-V drivers built in. In my case I need to run the same OS than my production server does.