Category Archives: system administration

Tape drives are obsolete

I was reading an article today that asks the question Are Tape Backup systems obsolete? I would say the answer is yes and that it has been that way for some time now.

Take google who build thier own commodity hardware. How would they ever back up so much data? Why would they even try? It would be much easier to just do what they are doing and replicate the data multiple places. Drives are becoming so huge how can you manage to keep up with your tape library solution? What if you had to back up the Sun Thumper at 24T? That would require a massive number of tapes.

We tried to use tapes for the longest time but the expense got to be too much. We were adding hardware left and right with drives that could fill an entire tape. After looking at autoloaders to cover the amount of data our graphics developers produce we gave up on tapes. That was two years ago. We went with Amanda's tapeless setup and a load of cheap hard drives that we could swap out for offsite backups. This setup has worked great. The cheap drives let us to expand our backup range from a couple weeks to month and longer if we wanted to. Having the extra space gave us the ability to back up user pcs if we needed to as well. As the size of drives for servers we buy increases so does are ability to expand our backup system. Moving to a hard drive based backup scheme has releaved us of the burden of waiting for tapes to catch up which they never seem to do.

backup, amanda, tape

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Sun ZFS and some big hardware

This is one large set of disks to have in only 4u of space. And to top it off the thing has 4 cores. I love commodity hardware and sun has been rolling out some nice commodity hardware these days. The price for some of the equipment has started to catch my eye now. I think as far as initial interest this file server would be great if they just had ZFS working for linux. It looks like they are trying to port it with FUSE as a Google SOC project. If they get it going it would probably fit in well with XEN.

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Virtualization gaining speed

At work we jumped on the virtualization wagon some time ago first when User Mode Linux and then later with Xen. UML was pretty good but Xen has been great. We had a few reasons for moving from physical machines to virtual ones:

  • Rack space is a recurring cost so maximizing the use of space is important. I have a philosophy of breaking up a lot of functions into their own servers. That is web servers shouldn't be also doing email for 1000 people.
  • Lots of people don't need the full power of a physical machine.
  • You can get a console for a virtual machine without having to visit the datacenter.
  • There is hope that at some point you may never need downtime since Xen and VMWare have the ability to do live migrations from one set of hardware to another. Upgrading a machine couldn't be easier.

Now it seems that more people are starting to move towards virtualization and Xen seems to have pushed things over the edge. I think a lot of that was interest generated because Xen was free and people could get their feet wet. That is probably what also drove VMWare to make part of their suite free. Xen is still not VMWare but it is gaining ground. There is support coming for Windows and Solaris with support for NetBSD already. The main gap I see in Xen's support is in the storage area. Before they can compete with VMWare at the highest levels they need to add better support for SANs or other distributed disk setups.

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WordPress permalinks with lighttpd (lighty)

WordPress out of the box works just fine with lighttpd. But you will run into issues if you want nice looking and search engine friendly URLs. To get that you need to turn on the non-default permalinks. Most of the information out there on how to set your webserver up to handle this is written for apache so if you are using lighttpd it is a little harder to find the correct way of doing the URL re-writing.

For more information about why you should use custom permalinks look here or here.

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Upgrade FC4 to FC5 with yum

I recently upgraded a bunch of FC4 (a few FC3) installs to FC5 using yum. It has been a long time since I've tried doing an OS upgrade like this because it used to be pretty painful. I was surprised at how easy it is to do now. There are a few issues to get past but for the most part for fedora core 4 to fedora core 5 you just have to follow a few simple steps:

  1. Remove any kernels before 2.6.14. There are packages that will not allow you to upgrade unless you do this step. Use the yum command: yum remove kernel-2.6.14* or the rpm command rpm -e kernel-2.6.14*
  2. Even though it isn't in the documentation I have had trouble in the past with some dependancies not working out correctly so I like to run "yum clean all" before starting the true upgrade.
  3. Install the fedora-release for Fedora Core 5. Use the rpm command: rpm -Uhv http://download.fedora.redhat.com/pub/fedora/linux/core/5/i386/os/Fedora/RPMS/fedora-release-5-5.noarch.rpm
  4. Run the yum update: yum -y update

That is all there is to it.

Technology brings us a particular happiness because it makes us happy through improvement, making the complex more and more simple, through the careful use of science, it makes us daydream. But they know what if it's ugly, not being able to sleep and dream really, so it's important that we know what is the best cheap melatonin brand. With this we can ensure our quality of sleep and sleep like Calderon de la Barca who tells us that dreams are dreams.

For more details see the following links:

YumUpgradeFaq and a good post on doing a FC4 to FC5 upgade.

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Cleaning up stale rails sessions (removing ruby_sess files)

I'm not sure if something isn't set up correctly of if this is just a fact of life with rails but the sessions it creates never seem to go away. I think before rails 1.1 the sessions where stored in /tmp and now they are stored in the apps directory along with everything else so they is probably no internal mechanism to delete them. I only noticed because after about a month of an certain app running the disk on the machine started to fill up. After digging a little I found 50K ruby_sess.* files hanging out in the rails session directory.

Anyway it was easy enough to clean up the stale ruby_sess files by going into the rails webapp/session directory and then running the following command:

find -type f -name "ruby_sess*" -exec rm -f {} \;

I'm not sure why the app is creating sessions but it isn't something that stores state so I didn't have to worry about killing active sessions here. If you do need to worry about that you will probably want to toss a time on the find command.

After looking a little more I found a post about this that has a ruby way of cleaning up the sessions.

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How to build the PHP rrdtool extension by hand

I think by now most sysadmin types know about rrdtool and the nice graphs it makes. I recently wanted to create some graphs by hand using PHP so I turned to the php-rrdtool extension. I found that it takes a little work to get it to compile but that could be because I'm not constantly recompiling PHP and just don't know better. You can get this module as an rpm for fedora (php-rrdtool) but I like to compile php by hand so I couldn't use it. I'm going to assume that you know how to compile PHP normally with whatever other items you want to include and that you have the rrdtool development libraries installed or have compiled and installed rrdtool from source.

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