Byte-aligning Linux partitions on modern disks

Linux uses 512-byte sectors. Hard disks used to too. The emergence of huge TB-sized disks has caused manufacturers to changed to 4096-byte sectors. This change can cause performance degradation on Linux as it's partitions may not be aligned with these bigger sectors. The additional overhead for the disk causes a performance drop.

This raises the need for aligning your Linux partitions to the new sector size. However, many tools such as fdisk and parted are not yet doing this for you easily. IBM DevWorks has a great in-depth article on the topic: Linux on 4KB-sector disks: Practical advice

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Tuning the nscd name cache daemon

I've been playing a bit with the nscd now and want to share some tips related to tuning the nscd.conf file. To see how the DNS cache is doing, use nscd -g. nscd configuration: 0 server debug level 26m 57s server runtime 5 current number of threads 32 maximum number of threads 0 number of times clients had to wait yes paranoia mode enabled 3600 restart internal passwd cache: no cache is enabled [other zero output removed] group cache: no cache is enabled [other zero output removed] hosts cache: yes cache is enabled yes cache is persistent yes cache is shared 211 suggested size <==== 216064 total data pool size 1144 used data pool size 3600 seconds time to live for positive entries <==== 20 seconds time to live for negative entries

Preventing PuTTY timeouts

Just found a great tip to prevent timeouts of PuTTY sessions. I'm fine with timeouts by the host, but in our case the firewall kills sessions after 30 minutes of inactivity... When using PuTTY to ssh to your Linux/Unix servers, be sure to use the feature to send NULL packets to prevent a timeout. I've set it to once every 900 seconds, i.e. 15 minutes... See screenshot on the right.

Setting up SR-IOV in RHEL6 on PowerEdge servers

Dell Community : "RHEL 6 provides SR-IOV functionality on supported hardware which provides near native performance for virtualized guests. Single-Root I/O Virtualization (SR-IOV) specification, introduced by PCI-SIG details how a single PCIe device can be shared between various virtualization guests. Devices capable of SR-IOV functionality support multiple virtual functions on top of the physical function. Virtual Function is enabled in hardware as a light weight PCIe function. Operating System cannot discover this function as it does not respond to the PCI bus scan and requires support in the host’s driver. As in PCIe pass-through, a Virtual function of a SR-IOV capable card can be directly assigned to the guest operating system. A virtual function driver running in the guest manages this device."

Oracle: Unbreak my Linux Heart

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