Archive
Posts from 2010
Why isn't Oracle using huge pages on my Redhat Linux server?
I am currently working on upgrading a number of Oracle RAC nodes from RHEL4 to RHEL5. After I upgraded the first node in the cluster, my DBA contacted me because the RHEL5 node was extremely sluggish. When I looked at top, I saw that a number of kswapd processes were consuming CPU: The kswapd process is responsible for scanning memory to locate free pages, and scheduling dirty pages to be written to disk. Periodic kswapd invocations are fine, but seeing kswapd continuosly appearing in the top output is a really really bad thing…
$ read more →Why oh why is grub eating CPU resources in a VirtualBox VM?
While reviewing the performance on my desktop today, I noticed that one of my VirtualBox virtual machines was consuming 100% of one CPU: This was somewhat perplexing, given that the host in question was sitting at a grub> prompt (I'm cleaning up my grub notes to post to my website, so stay tuned!). When I strace'ed the VirtualBox process (having a system encapsulated in a userland process makes debugging these types of issues super easy), I noticed that the process was issuing poll()s and read()s in a tight loop: At first I was perplexed by this, but upon further reflection this makes complete sense. The grub interpeter is executing a loop that polls the keyboard IO port for data, and continues to do so over and over again. Since most systems don't stay at the grub prompt for extended periods of time, the grub developers didn't use the HLT instruction to idle the CPUs when no actual work was being performed…
$ read more →Configuring and monitoring the T5220 hardware RAID controller
The Sun T5220 comes with a built-in RAID controller, which supports all of the standard RAID levels (0 - 6). Configuring one or more devices to participate in a RAID Configuration is dead simple, since you can use the Solaris raidctl utility. The last T5220 I configured had a root file system that was going to reside on the built-in RAID controller, so I had to boot into single user mode to create my volume. To create a RAID1 volume using the devices c1t0d0 and c1t1d0 (you can get the devices via format or raidctl), you can run raidctl with the "-c" (create raid volume) option, and the names of the disks to mirror: I also wanted to be able to use the cache on the RAID controller, which can be enabled using the raidctl "-p" (set property) option: Once I had a working RAID1 volume, I created a label on the device with fdisk and proceeded to perform a Solaris 10 installation…
$ read more →Awesome vSphere server videos
While I was studying for the VCP4 certification, I watched a number of awesome educational vSphere videos from Mike Laverick. Mike did a killer job with the videos, and they clearly explain a number of vSphere technologies in detail! Thanks a ton Mike for making these available!!!
$ read more →How to become a VMware certified professional (VCP4)
I passed the Vmware certified professional 4 (VCP4) exam this past Monday. The exam was a bit more difficult than I expected, though I passed it with flying colors. If you are thinking about taking the exam, or are interested in learning more about vSphere, you will definitely want to start out by reading Scott Lowe's Mastering VMware vSphere book. Scott did an excellent job putting the book together, and it's concise and easy to follow (I'm curious how Mike Laverick's vSphere implementation book compares to Scott's)…
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