Hi Lior
Don't know any detail of your configuration, check e.g. if it mentions a possible issue
http://www.cisco.com/c/en/us/products/collateral/servers-unified-computing/ucs-c-series-rack-servers/whitepaper-c11-734876.html
Note: Cisco does not support the installation of an SD card taken from a Cisco UCS C-Series server into a Cisco UCS B-Series server, or the reverse. Swapping SD cards from a rack server to a blade server, or the reverse, may result in data loss on the SD card. You may be able to reformat the SD card, but reformatting also results in data loss.
Configuring and Mirroring SD Cards in Cisco UCS Manager
FlexFlash SD cards are disabled by default. To configure and enable them, in Cisco UCS Manager, create a policy under Local Disk Configuration Policy within a service profile (see Figure 4).
Note: SD cards must be the same size for them to be mirrored. When FlexFlash is enabled through a local disk policy, the FlexFlash controller becomes enabled during service profile deployment. If a server does not support SD cards or is using a release earlier than IMC Release 2.2(1a), a configuration failure message is displayed.