Adventures in live booting Linux distributions

We’re all familiar with live booting Linux distributions. Almost every Linux distribution under the sun has a method for making live CD’s, writing live USB sticks, or booting live images over the network. The primary use case for some distributions is on a live medium (like KNOPPIX). However, I embarked on an adventure to look at live booting Linux for a different use case. Sure, many live environments are used for demonstrations or installations - temporary activities for a desktop or a laptop....

2014-07-29 · 5 min · Major Hayden

Dual-primary DRBD with OCFS2

As promised in one of my previous posts about dual-primary DRBD and OCFS2, I’ve compiled a step-by-step guide for Fedora. These instructions should be somewhat close to what you would use on CentOS or Red Hat Enterprise Linux. However, CentOS and Red Hat don’t provide some of the packages needed, so you will need to use other software repositories like RPMFusion or EPEL. In this guide, I’ll be using two Fedora 14 instances in the Rackspace Cloud with separate public and private networks....

2011-02-14 · 4 min · Major Hayden

Keep web servers in sync with DRBD and OCFS2

The guide to redundant cloud hosting that I wrote recently will need some adjustments as I’ve fallen hard for the performance and reliability of DRBD and OCFS2. As a few of my sites were gaining in popularity, I noticed that GlusterFS simply couldn’t keep up. High I/O latency and broken replication threw a wrench into my love affair with GlusterFS and I knew there had to be a better option....

2010-12-03 · 3 min · Major Hayden

Switching from GlusterFS to DRBD and OCFS2

As my uptime reports have shown, and as some of you have reported, my blog’s load time has increased steadily over the past few weeks. It turns out that one of my VM’s was on a physical machine that had some trouble and I was reaching a point where GlusterFS’s replicate functionality couldn’t meet my performance needs. Instead of using GlusterFS as I had before in my redundant cloud hosting guide, I decided to use DRBD in dual-primary mode with OCFS2 as the clustering filesystem on top of it....

2010-11-10 · 1 min · Major Hayden

GlusterFS on the cheap with Rackspace’s Cloud Servers or Slicehost

NOTE:This post is out of date and is relevant only for GlusterFS 2.x. *High availability is certainly not a new concept, but if there’s one thing that frustrates me with high availability VM setups, it’s storage. If you don’t mind going active-passive, you can set up DRBD, toss your favorite filesystem on it, and you’re all set.If you want to go active-active, or if you want multiple nodes active at the same time, you need to use a clustered filesystem like GFS2, OCFS2 or Lustre....

2010-05-28 · 4 min · Major Hayden

ext3_dx_add_entry: Directory index full!

I found a server last week that was having severe issues with disk I/O to the point where most operations were taking many minutes to complete. The server wasn’t under much load, but a quick run of dmesg threw quite a bit of these lines out onto the screen: EXT3-fs warning (device sda5): ext3_dx_add_entry: Directory index full! After a thorough amount of searching, I couldn’t find out what the error actually meant....

2008-10-13 · 1 min · Major Hayden

What is the difference between file data and metadata?

Just in case some of you out there enjoy nomenclature and theory behind Linux filesystems, here’s some things to keep in mind. The modification time (mtime) of a file describes when the actual data blocks that hold the file changed. The changed time (ctime) of a file describes when the metadata was last changed. Also, metadata is stored within a different location than the data blocks. The metadata fits in the inode while the file’s data goes within data blocks....

2008-03-12 · 1 min · Major Hayden

EXT3-fs error (device hda3) in start_transaction: Journal has aborted

If your system abruptly loses power, or if a RAID card is beginning to fail, you might see an ominous message like this within your logs: Basically, the system is telling you that it’s detected a filesystem/journal mismatch, and it can’t utilize the journal any longer. When this situation pops up, the filesystem gets mounted read-only almost immediately. To fix the situation, you can remount the partition as ext2 (if it isn’t your active root partition), or you can commence the repair operations....

2007-11-20 · 1 min · Major Hayden