HP Storevirtual 4000 White Paper

12
Technical white paper | HP StoreVirtual 4000 Storage
Flow control
Flow control should be enabled on all switch ports that handle iSCSI trac to prevent buer overow. HP Networking
switches recommended in Table 5 support both send and receive pause frames.
Nice-to-know
• Flow control is a temporary means of congestion management and is not a resolution for switch backplane
oversubscription. Flow control utilizes the buer of the sending switch for a brief period to manage the switch buer of
the receiving switch during period of congestion.
• Some switch manufacturers do not recommend conguring ow control when using jumbo frames, or vice versa.
Consult the switch manufacturer documentation for guidance on this issue.
• Some manufacturer switch models may have limited ow control support, that is, the ability to receive and respond
to pause frames, but do not support the ability to send pause frames. HP Networking series of switches listed in Table
5 can respond to pause frames generated by targets and initiators, allowing them to control the overall data ow
between servers and storage volumes.
Best practices
• HP recommends enabling ow control, ow control should be enabled on all switch ports.
Jumbo frames
When using jumbo frames for the iSCSI network, all switch ports on the network segment need to be congured for
jumbo frames. If the ports are not properly congured, the switch may discard frames. This may cause connectivity and
performance issues, which are dicult to troubleshoot.
Nice-to-know
• Jumbo frame sizes are not standardized across all switch manufacturers.
• On HP Networking switches, jumbo frames can be enabled globally, per-VLAN and or on a per port interface basis.
• Switches that don’t support jumbo frames, drop jumbo frames.
Best practices
• For a jumbo frame to be transmitted in whole from end to end, every network device within the network path must
support that frame size.
• When employing jumbo frames in iSCSI networks, remember to set the MTU on access, trunk, EtherChannel or LACP
ports appropriately for all ports within the iSCSI data path.
• HP doesn’t recommend the use of jumbo frames for all customer deployments. However, depending on the
characteristics of the iSCSI workloads, HP test results have shown a performance gain of 10–20 percent
3
when
designed and congured properly for large sequential read and write workloads.
3
HP performance engineers in Fort Collins, CO, USA; June/July 2012

HP Storevirtual 4000 Specifications

General

Brand	HP
Model	Storevirtual 4000
Category	Storage
Language	English