Use of HP FlexFabric 10Gb 2-port 534FLB Adapter in a vSphere design using dependent hardware iSCSI mode.
Need to find out the number of outstanding iSCSI I/Os that the adapter can handle, to ensure that number of concurrent SCSI commands has been taken into account.
HP FlexFabric 10Gb 2-port 534FLB is based on Broadcom 57810S chipset which uses the bnx2i driver/firmware (see March 2014 VMware FW and Software Recipe)
Broadcom’s bnx2i iSCSI driver is dependent hardware iSCSI (see Cormac Hogan excellent blog post on vSphere 5.1 Storage Enhancements – Part 5: Storage Protocols)
A dependent hardware iSCSI adapter is a third-party adapter that presents itself as a normal NIC, but has an iSCSI offload engine. It requires the use of VMKernel interface, which is then tied to the vmhba (HBA).
The following applies to the Broadcom 57810S chipset:
- Total outstanding iSCSI Tasks (I/O) per port = 4096 (4K)
- Total iSCSI Sessions per port = 128 – 2048 depending on the Operating System (Host limited)
Each iSCSI Session facilitates communication with a different Target:
- Total of 512 outstanding iSCSI Tasks (I/Os) per Session
Therefore using HP FlexFabric 10Gb 2-port 534FLB Adapter we can have 1024 outstanding iSCSI Tasks across two adapters of 512 each.