Slight delays on the second installment of the present series. “When Observation and Scripture collide”. I lost a few files, including my rpm database when my testing version of Fedora came a cropper. I was running Logical Volume Management on top of a RAID 0 (striped) disk array, and things got a busy on the bus when I tried to burn a DVD.
Logical Volume Management (LVM) is cool because you can dynamically resize partitions, and even span partitions across physical disks, allowing you a lot more flexibility for reconfiguring your system as your needs change. The other way cool thing with LVM is that you can take a “snapshot” of a partition at a certain point in time and use that to make a backup. This is useful for obtaining consistent backups of systems in production, especially databases, such as the World Sankirtan.Net servers, which is where my interest lies.
The RAID 0 thing is just about raw speed. The hard disk is the slowest component in the computer. While everything else is all about electrons - the hard disk is about motors, heads, and magnetic platters. By using two hard disks and “striping” the data across them, one disk is seeking while the other reading. Voila, less time spent waiting for the hard disk to get back to us.
Fedora Linux supports both LVM and RAID 0 in the kernel. I not sure what’s going on with my system yet, but I can’t read DVDs without crashing the system or burn CDs or DVDs reliably. I de-LVM and de-RAIDed the system and am opting for stability (which right now also means no DVD or CD/DVD burning).
The next step, once things stabilize a little for me with the Fedora test, is to do RAID 0+1 with XFS. The guys at work tell me that the XFS filesystem is noticably faster than ext3, although it doesn’t have as robust error recovery. RAID 0+1 means striping and mirroring. It’s gives RAID 0 performance for reads, and is slightly slower than normal for writes.
I’ll be rewriting the second installment of the series before I go doing any other changes to my system, don’t worry about that. Expect it in the next few days.
