Viewing CPU frequency scaling data on CentOS Linux hosts
I just built a new quad core AMD Opteron host, and was curious what frequency steppings were available for my processor. After a bit of poking around, I came across the cpufreq-utils package, which contains utilities to view and set processor frequency settings. To view the settings for the processors on a system, cpufreq-info can be run without any options (this assumes you installed the cpufreq-utils package): The output above contains the list of frequency steppings: As well as the current operating frequency of each core: If you want to change the frequency profile for a processor, you can use the cpufreq-set utility. I should use this as an opportunity to pick up a kilowatt, and see how much energy is being saved by running the CPUs at 1.1GHZ instead of 2.2GHZ.
$ read more →Debugging problems with the open-iscsi initiator
I talked about the open-iscsi initiator in a previous post, and briefly touched on debugging problems. If you want to get additional debugging data for the iscsid daemon, you can add the "-d 8" option to the iscsi initialization file: This will cause the daemon to write a bunch of debugging data to the syslog logs, which you can then use to isolate problems.
$ read more →Best I/O scheduler to use with virtualized Linux hosts
While reading through the Redhat Oracle 10G best practices document, I came across this gem: "In virtualized environments, it is often detrimental to schedule I/O at both the host and guest layers. If multiple guests access storage on a file system or block devices managed by the host operating system, the host may be able to schedule I/O more efficiently because it alone is aware of requests from all guests and knows the physical layout of storage, which may not map linearly to the guests' virtual storage. Red Hat Enterprise Linux 4 and Red Hat Enterprise Linux 5 guests can use the noop I/O scheduler to allow the host to optimize I/O requests." This makes complete sense, and I am going to have to test out the noop I/O scheduler in my lab this weekend. I'm curious how many folks run the default I/O scheduler in their Xen or KVM guests, and are actually hindering I/O performance by doing so.
$ read more →Updating Emulex firmware on Solaris hosts
I've written about the Emulex emlxadm utility in the past, and how it can be used to view and manage adapters. In addition to viewing stats and configuration data, you can also use emlxadm to view and update firmware. To view the current firmware version, you can type "get_fw_rev" into the emlxadm shell: If the firmware needs to be updated, you can run download_fcode with the path to the firmware image: This post is a reference for myself, and I take ZERO responsibility for botched firmware updates. As with all information on this blog, use this information at your own risk (no warranties of any sort are provided).
$ read more →Changing the IP address on a Brocade 3200
I purchased a used Brocade 3200 for my home lab, and needed to update the network information to allow myself to login remotely. To view the existing network configuration, I serial consoled in and ran the ipAddrShow command: Once I checked the existing settings, I ran the ipAddrSet command to update the network settings: I really dig Brocade, and their command set is simple and easy to use.
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