Sneak Preview: Red Hat Brings Power At A Price
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Productivity, security and stability are at the core of the latest version of Red Hat’s Enterprise Linux. I tested the Release Candidate model of RHEL 4 in our Green Bay, Wis., Real-World Labs® and our NWC Inc. business applications labs, and verified the soundness of some of its new features.
RHEL 4 includes modifications to the virtual memory and I/O sub-system, as well as a more generic logical processor task scheduler that accommodates both hyperthreaded and multicore technologies. Not only can administrators use larger disk partitions, they also can choose an I/O schedule to optimize server performance based on the applications being deployed. RHEL 4’s core setup options include:
• CFQ (Complete Fair Queue) Scheduler. Manages I/O requests and bandwidth on a per-process basis; good for workloads requiring low latency and high throughput.
• Deadline scheduler. Gives I/O requests a deadline by which they must be served; best for applications like databases that require frequent disk access.
• Anticipatory scheduler. Extends the deadline scheduler by adding heuristics that reorder I/O access and increase throughput.
• No-op scheduler. Schedules I/O requests without any algorithmic preference for one request over another; optimal for a virtualized environment that takes advantage of an existing scheduler.
RHEL 4 uses the Ext3 file system and has added enhancements surrounding file access and synchronization. Also included in this release is LVM2 (Logical Volume Manager 2), which lets you manipulate files systems. I tested this feature using the CLI (command-line interface) and found it effective and easy to use. For example, I used lvreduce within LVM2 to decrease the size of LogVol01 from 1.94 GB to 1.84 GB with a single command. Next, I used lvextend to bring it back to its original size.
A full suite of command-line tools lets you manipulate each logical volume in a volume group, which surely beats symbolically linking directories to alternate file systems when you run out of room. But beware: The tools can be dangerous. Indeed, they’ll warn you that decreasing the size of a volume may result in data loss.
