Category Archives: hardware

All things hardware related

how-to: cloning a boot from SAN RHEL LUN

Some prep work goes into setting up a good boot from SAN LUN for use in deploying new physical systems however once you have a well defined structure of LVM and standard disks, the process of cloning a boot LUN can easily be scripted. Here’s the basic steps that go into updating your kernel once you’ve cloned a boot disk.
Some things to keep in mind when preparing a LUN to clone to other systems:

  1. Try to keep the number of LUNs required for the system to boot to 1. This will ensure there are less edits required to update your initrd image.
  2. Avoid cloning a LUN that has multiple volume groups with more than 1 SAN LUN. As of RHEL 5.7 (2.6.18-274.x kernel) udev has problems utilizing a system volume group when say and application volume group (with separate physical disks) is missing.
  3. Prior to cloning your system, update your multipath.conf so that your bindings file is located on the root partition and not on a separate partition as so:
    bindings_file /etc/bindings

Post clone steps for updating your initrd image with the scsi ID for your new boot disk:
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Asus P6T RAM/stability problems

I purchased a P6T with 6GB of RAM a while back when I decided I wanted to upgrade to 12GB of RAM.  Here’s an interesting tidbit about the P6T, your RAM timings have to be the same or you’re going to have stability problems.  The stability problems will problems will present themselves as issues like this or this.  After returning the motherboard several times, I finally spoke to a third level engineer who politely explained to me why the motherboard would randomly detect 10GB or 8GB of RAM.  He explained that the issue was caused by 3 sticks of my memory having timings of CL8 and the other three with timings of CL9.  I did not believe it until I purchased 12GB of CL8 matching memory and have since had no stability problems and the motherboard detects all 12GB of memory.

On a side note I do not think it is necessary that someone (Much like myself) return a motherboard three times (One time the replacement motherboard came with 2 faulty PCI slots) before they get to a technician that can explain the situation.  Needless to say, I can neither recommend nor will I purchase Asus products in the future (Mostly because of poor support practices).