Monthly Archives: September 2011

Updating the bios on a Dell PE 860 using USB

Sorry, this is going to be brief:

  1. Use unetbootin to put freedos on a USB stick
  2. Download the BIOS update from the Dell site (use the unpackaged version), copy to the root of the USB drive and rename to install.exe
  3. Boot the Dell machine to the USB stick (see previous post for details on this)
  4. When you’ve reached the FreeDOS boot menu, choose “FreeDOS Live CD with HIMEM only” (live CD only and HIMEM + EMM386 didn’t work for me)
  5. Change to the USB stick (should be “c:”)
  6. Install the new BIOS (“install”)

Booting the Dell PE 860 from USB

Plug in the USB stick, then in the bios:

Integrated Devices -> make sure USB Controller is “On with BIOS Support”
USB Flash Drive Emulation Type -> should be “Hard disk”
<reboot>
Hard-Disk Drive Sequence -> make sure the “Hard-disk-emulated USB flash drive” is first
<reboot>

Should now boot into USB (if you remove the USB at some point after setting the hard drive sequence it seems to change it back to actual hard drive over USB, so if you remove it and plug it back in to boot from it again, you’ll need to go back into the BIOS to change the setting again).

Switching from load-balancing to active-backup on XenServer

By default, the NIC bonding in XenServer is load balancing (SLB); apparently every 10-30 seconds it switches the NIC it’s using, and the default setting is an up-delay of 3.1 seconds** (see here).

To change to active-backup, you need to do the following (this requires a reboot by the way):

  1. Have your bonds set up in XenServer (use the XenCenter GUI)
  2. Find the UUID of the bond (something like: bd25429f-f7ff-3206-e5b2-4c027c51947c)
    1. Get the network UUID of your bond: xe network-list
    2. Get the pif UUID by matching the network-uuid parameter with the one you found in the step above: xe pif-list
  3. Run the following command: xe pif-param-set uuid=<bond_pif_uuid> other-config:bond-mode=active-backup
  4. Reboot the XenServer
  5. Check your bond settings: cat /proc/net/bonding/bond0; the Bonding Mode should say “fault-tolerance (active-backup)”

I’ve not yet figured out how to set a primary NIC for the bond (it’s not officially supported*), will report back when have done.

 

*UPDATED: found this “Can be configured with one fast path, and one slow path for cost savings; in this scenario, the slow path should only be used if there is a failure on the fast path” – but that’s the only documentation I can find about it, so it may or may not be officially supported…Ref: http://support.citrix.com/article/CTX124421

**UPDATED: in the admin manual, they say this about the up-delay:
“Bonding is set up with an Up Delay of 31000ms and a Down Delay of 200ms. The seemingly
long Up Delay is purposeful because of the time taken by some switches to actually start
routing traffic. Without it, when a link comes back after failing, the bond might rebalance
traffic onto it before the switch is ready to pass traffic. If you want to move both connections
to a different switch, move one, then wait 31 seconds for it to be used again before moving
the other.”

It also says that XenServer supports Active-Passive NIC bonding which is derived from active-backup (ie, they state that it’s not actually active-backup), and that a fast path and slow path can be configured.  However, the steps to configure active-passive state to use “other-config:bond-mode=active-backup” (so the steps above are correct, only they set the server to XenServer’s implementation of active-backup which they call active-passive).  The manual also doesn’t mention how to configure the fast and slow paths, and while it lists PIF commands, it doesn’t even mention the other-config:bond-mode command…