Dell EqualLogic PS6210E EqualLogic Host Integration Tools for Linux Version 1. - Page 10
PS Series Group Network Recommendations
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• SD block device-Disk block devices for iSCSI; a direct connection between a host and a PS Series group member • Smart Copy-A snapshot, clone, or replica of an individual volume or component, or a collection of volumes or components • Switch device-A top-tier switch device for each volume. The host system uses the dm-switch driver to log in to the device and then route I/O to the appropriate multipath device • Volume slice-The portion of a volume that is located on a single member For additional terminology specific to Dell EqualLogic storage products, see the Dell EqualLogic Master Glossary. PS Series Group Network Recommendations The following table describes the network recommendations for PS Series group operation and for computer access to the group. All the normal networking rules apply; however, network configuration is beyond the scope of this manual. Table 1. PS Series Group Network Recommendations Recommendation Switched Gigabit Ethernet network Description Connect arrays and computers to a switched network. Dell recommends that all network connections between computers and arrays are Gigabit Ethernet. (An array can operate at 10 and 100 Mbits, but performance will be significantly degraded.) Network interface cards (NICs) or host bus adapters (HBAs) must operate at a minimum of 1 gigabit per second (1 Gb/sec). NICs that operate at speeds of less than 1 Gb/sec are not used for multipath I/O by default. Network switch types Multiple network connections Dell recommends using enterprise class switches of a nonblocking design for your iSCSI SAN. If using multiple switches, link the switches to enable communication across different subnets. Use a link of sufficient bandwidth. For increased bandwidth and availability, connect multiple network interfaces on an array to the network (use different switches, if possible). Connect the interfaces from lowest port (port 0) to the highest. At least two network connections are required for multipath I/O. The initial group setup configures only one network interface on an array (port 0). After creating the group, use the Group Manager GUI or CLI to assign an IP address and netmask to other network interfaces. Access to the group IP address In a multisubnet group, each configured network interface should have access to the subnet on which the group IP address resides. Redundant network paths Multipath I/O provides a highly available network path between computers and arrays. For replication, a reliable, adequately sized For effective and predictable replication, make sure that the network link between the network link primary and secondary groups is reliable and provides sufficient bandwidth for copying data. Flow control enabled on switches and NICs Enable flow control on each switch port and NIC that handles iSCSI traffic. PS Series arrays will correctly respond to flow control. Unicast storm control disabled on switches Disable unicast storm control on each switch that handles iSCSI traffic, if the switch provides this feature. However, the use of broadcast and multicast storm control is encouraged on switches. Jumbo Frames enabled on switches and Enable jumbo frames on each switch and NIC that handles iSCSI traffic to obtain NICs performance benefits and for consistency of behavior. No STP functionality on switch ports that connect end nodes Do not use spanning-tree (STP) on switch ports that connect end nodes (iSCSI initiators or storage array network interfaces). If you want to use STP or RSTP (preferable to STP), you should enable the port settings available on some switches that let the port immediately transition into STP-forwarding state upon linkup. This can reduce network interruptions that occur when devices restart, and should be enabled only on switch ports that connect end nodes. Dell recommends using spanning-tree for a single-cable connection between switches and trunking for multicable connections between switches. 10 Introduction to HIT/Linux