Queue Depth and the FBWC Controller Cache module on the Cisco 12G SAS Modular Raid Controller for Virtual SAN

If you scan the bill of materials for the various Cisco UCS VSAN ReadyNodes you’ll see a line item for:

Controller Cache: Cisco 12Gbps SAS 1GB FBWC Cache module (Raid 0/1/5/6)

If you’ve followed Virtual SAN for awhile you might wonder, why would the ReadyNodes include controller cache when VMware recommends disabling controller cache when implementing Virtual SAN. Well, it turns out that the presence of the FBWC Cache module allows the queue depth of the Cisco 12G SAS Modular Raid Controller to go from the low 200’s to the advertised 895. The minimum queue depth requirement for Virtual SAN is 256 so including the FBWC Cache module allows the queue depth to increase above that minimum requirement and improve Virtual SAN performance.

2 thoughts on “Queue Depth and the FBWC Controller Cache module on the Cisco 12G SAS Modular Raid Controller for Virtual SAN

  1. Good tip… I was wondering about that.

    Cisco also sells a non RAID version of the 12G SAS controller card, called HBA or Pass-through (part number UCSC-SAS12GHBA). It obviously has no cache but is listed on the VSAN HCL as having a queue depth of 600.

  2. Good tip… I was wondering about that.

    Cisco also sells a non RAID version of the 12G SAS controller card, called HBA or Pass-through (part number UCSC-SAS12GHBA). It obviously has no cache but is listed on the VSAN HCL as having a queue depth of 600.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s