Category Archives: Linux

Network Switches and Data Transfer Speeds

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I recently upgraded my home network from 100 Mb/s to 1 Gb/s by replacing the switches. The main house switch is an unmanaged 1U rack-mounted switch, with a second desktop switch. Out of pure interest, I took the opportunity to do a little bit of speed testing to see how much of a difference upgrading the switches made in terms of actual data transfer speeds.

A few basics to avoid confusion  – b/s is bits per second and B/s is bytes per second. All of the reported figures will be in MB, so converting b/s to B/s:
Fast Ethernet = 100 Mb/s = 12.5 MB/s
Gigabit Ethernet = 1 Gb/s = 125 MB/s

100 Mb/s and 1 Gb/s refer to the speed of the underlying technology but data transfers at these rates are never achieved because of protocol overheads and such. As a baseline, if I write a large file (8 GB) to my PC’s local disk, I get a data transfer of between 50-55 MB/s.

On my network, I have two Buffalo Linkstation NAS devices, one with a Fast Ethernet interface and one with a Gigabit Ethernet interface. 2 GB’s worth of data would be written to each of these devices with different Ethernet switches in place to see what actual data transfer speeds would be achieved. The following Linux command was used five times in each situation and the result averaged.

time dd if=/dev/zero of=testfile bs=16k count=16384
Switch Model Data Rate to Fast NAS Data Rate to Gigabit NAS
1U Rack
Dynamode SW240010-R(Fast) 6.2 MB/s 8.6 MB/s
TP-Link TL-SG1016 (Gigabit) 6.4 Mb/s 21.4 MB/s
Desktop
D-Link DES-1008D (Fast) 6.2 MB/s 8.6 MB/s
Netgear GS605 (Gigabit) 6.5 MB/s 21.1 MB/s

I also carried out two further tests:

  1. With Gigabit Ethernet only, I wrote to both NAS devices at the same time. The data transfer speeds were unaffected.
  2. I connected the two Gigabit Ethernet switches in series and wrote to the NAS. Transfer speeds were reduced by 1 MB/s on the Gigabit NAS to 20 MB/s. The change on the Fast Ethernet NAS was minimal.

There are several things that can be deduced from the information shown in the table above and the other tests.

  1. Actual data transfer rates are considerably less than the theoretical maximums.
  2. There’s no performance difference between rack-mounted and desktop switches.
  3. The write speed of the NAS can be a limiting factor.
  4. Gigabit Ethernet switches give large improvements with Gigabit Ethernet devices.
  5. Gigabit Ethernet switches give small improvements even with Fast Ethernet devices.
  6. Keep the number of switches in the network path to a minimum.

 

The Best Ever SuSE Linux – v11.4

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OpenSuSE 11.4 was released back on 11 March so this weekend I took the plunge and upgraded my main PC from 11.3 to 11.4. And less than two hours later, I had the best ever SuSE running on my PC.  Here’s how I got on…

SuSE offer two methods of upgrading, the first being an on-line update and the second being the more traditional iso image download, burn and boot. I chose the latter as the guidance on SuSE’s website suggested that this would be more reliable. It also means that if the upgrade does fail and I needed to carry out a complete install from scratch, I already had the media to hand. Before booting from the DVD to upgrade, I backed up all the user files from the home partition and made copies of the important files – fstab, hosts, passwd, groups, auto.nas and so on.

Booting from the DVD, the installer goes through the usual licensing screen before analysing the existing system. As I had 11.3 previously installed, the installer gave me the option to upgrade, which I choose. After more analysis, it gives a summary of the changes required before asking permission to proceed – which I gave.

About 35 minutes and 250-odd packages later, the PC rebooted, loaded Linux and displayed the login screen. I entered my username and password, and the screen faded to the X desktop, with all my icons and widgets still there. Sweet!

Even more surprisingly, all the 3D window effects worked out of the box. That’s never happened before – normally you have to download drivers from nVidia or ATi before all the graphic goodness works smoothly. To be fair 11.3 was a “nearly” release. While the applications and tools worked, the 3D effects were a bit hit or miss. Sometimes they worked, sometimes they didn’t. But 11.4 hits it on the head.

The 3D eye candy is very slick. I run a 3 x 2 virtual desktop and the scrolling between the desktops is super-smooth, making it feel like one giant desktop. Windows glide in and out as they open and close. But by far my favourite effect is when you have overlapping windows and you want to bring one to the foreground. The upper window slides down the screen and then slips behind the lower window, bringing it to the front. Think of taking off the top sheet from a pile of paper and putting it to the back. So cool.

I’ve taken a couple of screenshots but (a) it’s really hard to catch the window closing when pressing the PrtScn button and (b) there’s no sense of the animation.

To finish off the installation, I added the ubiquitous Packman repository to load up all the unofficial multimedia goodies, such as DVD playing and video encoders.

Although it’s only been a few days, I’ve not encountered any problems at all with 11.4 and I’ve discovered that several of 11.3’s bugs have been fixed. Most of the major packages have been updated and OpenOffice.org has been replaced by LibreOffice (which is a whole sorry story in itself). Everything seems to be working fine.

If you want to try SuSE without messing with your current setup, there are live DVDs available for download. I run the KDE desktop rather than Gnome.

While it may be a little premature, I think this is the best SuSE ever.

OpenSuSE Linux 11.4 Released

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The latest version of OpenSuSE Linux, 11.4, has just been released and it’s chock full of new features. The replacement for OpenOffice.org, LibreOffice, gets its first major outing, KDE gets bumped to 4.6 and Gnome comes in at 2.32.

There’s a also a pile of updates to applications, including Empathy, RhythmBox, Amarok, Totem, Evince and Shotwell. For developers, GTK 3 is included so Gnome applications can be upgraded to the new framework.

I’m running 11.3 so I’ll be downloading from the mirrors tonight and upgrading over the weekend. I’m looking forward to the new eye candy provided by the KDE Plasma Desktop Workspaces. Ok, so I’m shallow.

If you want to try OpenSuSE, there’s a live version as well, in both KDE and Gnome flavours. Give it a whirl.

Goodbye Ubuntu, Welcome Back SuSE

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Some of you may recall that early last summer, I left my long-term Linux partner OpenSuSE for Canonical’s Ubuntu – the post is here. I thought it was going to be forever but I’m afraid it hasn’t worked out and SuSE has taken me back.

The original problem was that I couldn’t get SuSE 11.2 to install on new hardware and while Ubuntu 10.04 happily installed onto the new motherboard and harddrives, it’s been the legacy hardware that has been the root of the problem. Specifically, applications that wanted to access my SCSI scanner had to run as root, I completely failed to pull DV video from a video camera over Firewire and I couldn’t configure, never mind watch, my TV card. Scouring the newsgroups, I wasn’t alone. Perhaps naively, I thought that these problems would be fixed with Ubuntu 10.10 but alas, they persisted.

During the Christmas holidays I’d finally had enough – I can’t remember what finally caused me to snap but I downloaded OpenSuSE 11.3, burnt the DVD and rebooted. This time I didn’t encounter any of the previous problems from 11.2 and the installation went smoothly. It was like coming home – everything worked. Scanner – check, DV – check, TV – check.  And although returning to KDE desktop from Gnome, I have decided to keep some of the Gnome-based apps in preference to the KDE equivalents. gPodder is now my default podcatcher and Amarok has been replaced by RhythmBox.

It’s interesting times for OpenSuSE. In November, parent company Novell was sold to Attachmate but allegedly it’s business as usual. Version 11.4 will be out in a few weeks too.

There’s no doubt that some parts of Ubuntu were very seductive, such as package management, but I’m sorry Ubuntu…you’ve been dumped.

Amarok & KDE Crash Reporting – FAIL

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Sigh. I love Linux but there are times when you realise it’s never going to take over the world…

I was working with Amarok, but the program crashed completely every time it hit a certain file in my audio library. This wasn’t a big deal but being a helpful soul, when I was presented with the option to send crash information back to the coders, I clicked on “Ok.”  And this is where it all went wrong.

First of all, after showing the stack trace (whatever that is), the crash handling dialog tells me that it’s not much use without the debug symbols, but the package to do that isn’t installed.  Did I want to install the necessary package?  So I said, “Yes,” still being a helpful soul.

Next, an error pops up saying that it can’t find the package and could I add a repository via the package manager?  Of course, the error message doesn’t tell me either the package that’s needed or the name of the repository needed. Being an ever-helpful soul, I figured out by myself that I need to enable the debug repository in the package manager, after which the crash handler was able to load the package and add the debug symbols. Hurrah!

So I hit  “Next” and I get presented with a username and password dialog for the KDE bug database. Apparently I can only log crashes if I’ve registered with the bug database. At this point I gave up being a helpful soul and closed the dialog.

So, for Amarok and KDE developers, here’s a clue. If you want feedback from your users on what’s going wrong with your applications, don’t make it so hard to give the information. Having agreed to give the feedback, that should be it, job done. I should not have to install a package, configure a repository and get a username for some website I’m never going to visit.

Even Dr Watson wasn’t this stupid.

WobZIP, An Online Unzipper

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Have you ever downloaded some data off the ‘net only to find it’s in a compressed or archive file format that your PC doesn’t have a helper app for? Or you’re fixing up a friend’s PC, you download some drivers and ditto, you can’t get them unpacked?

If so, you’ll be interested in WobZIP. It’s a web site where you can upload an archive file and it will uncompress it for you.  Once uncompressed, you can either download the files one by one, or else the site will bundle the files back up into a zip archive for you to download.

The site is still in beta but claims to support the following archive formats – 7z, zip, gzip, bzip2, tar, rar, cab, iso, arj, lzh, chm, z, cpio, rpm, deb and nsis.  Obviously quite a few of those formats are Unix and Linux, but there’s a fair collection of DOS / Windows ones too.  As it’s a website, it doesn’t care what OS you’re running either. From the FAQ, WobZIP uses the open source 7-zip program as the decompression engine.

Cleverly, there’s also a feature to unpack or uncompress from a URL so you don’t always have to download to your PC and then upload back to WobZIP – you can just enter the URL and it will go and get the file for you.  Also, it will scan the unpacked files for viruses.

Put this site in your bookmarks.  You may not need it right now, but you will one day.

Ubuntu 10.10 Released 10/10/10

Linux,

The latest version of the Ubuntu Linux distribution, 10.10 will be released tomorrow (if all goes to plan). Otherwise known as the Maverick Meerkat, this release focuses on improving the desktop experience and stability rather than radically updating it.

As usual, the kernel has been updated along with the Gnome desktop and there has been one change to the default apps (Shotwell for F-Spot in photo management) but apart from that, it’s pretty much upgrades and improvements.  Allegedly boot times have been improved as well, but 10.04 already booted pretty quickly.

If you haven’t figured out from the post title, Ubuntu releases aren’t numbered by simply incrementing versions.  The numbers are the year and month that software was released in thus October 2010 is 10.10.  The last release, Lucid Lynx, came out in April of this year so is 10.04.

As a further joke, this release is coming out on 10/10/10 which in binary is 42, homage to Douglas Adams’ answer to the meaning of life, the universe and everything.

I’ll report back on how my upgrade goes.