Reporting from the Field Issue #1 – Cisco UCS-B FlexFlash Pairing

As I continue to roll out Cisco UCS, i’m beginning to see a trend of moving away from Boot from SAN deployments to internal SD card Hypervisor installations.  The arguments are there to justify the additional cost in purchasing dual FlexFlash modules instead of “wasting” space on your expensive Storage Array.

There is also a lot of deployments that we are doing on NFS, Boot from SAN is not supported on NFS.

For the UCS Manager savvy, you should already have an understanding of what a Local Disk Policy is, for those that aren’t…let me explain.  Simply put, the Local Disk Policy sets the configuration of how your local disks should be configured on your UCS Servers.  In half-width blades, you have two 2.5″ drive slots that can be set for multiple RAID types, no RAID, etc.  Full width blades have 4 disks which allow additional RAID options like RAID 5 etc.  SD cards are treated differently as you’ll see below.


With the FlexFlash modules you can set them to mirror in UCS Manager on B series it’s a bit tricky.  I was under the impression that these would be treated like any other local disk and that I could choose a RAID1 Mirror setting for them.  I was totally wrong.

For FlexFlash Mirroring you have to create the Local Disk Policy as configured here:


Then you have to configure a Scrub Policy.  Yeah..I was scratching my head as well.  The Scrub Policy will complete the pairing of the SD cards and wipe the HV partition on each and brings them to a healthy RAID state.  Keep in mind you only need to apply this when initially installing two SD cards, or if you need to add an SD card to a current install on a Single SD card to complete the pairing.


Lastly, create a Boot Policy that will allow booting from the SD Cards.  Notice I always put in a CDROM as my first boot device, this should be standard on all Boot policies so that you can install from Media or ISO image mounts via KVM.


Remember, when you are done with pairing, remove the Scrub Policy.

More information can be found in the Cisco UCS Manager GUI Config guide for 2.2.

One thought on “Reporting from the Field Issue #1 – Cisco UCS-B FlexFlash Pairing

  1. Hi Mike. Thanks for the helpful screenshots. I was wondering…after pairing the SD cards, if one of the SD cards fails/goes bad and you need to replace it, do you have to go through the scrub/no-scrub process again to re-pair the SD cards? Basically, do you have to wipe out the installation on the surviving SD card any time you need to re-pair it with another card? I’m new to UCS…

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