A very common misperception is that iSCSI SANs are not as secure as Fibre Channel SANs. In fact, when logically or physically separated, iSCSI networks are just as secure as Fibre Channel.
iSCSI is sending SCSI commands in IP packets. To be more specific, iSCSI is designed to be a protocol for a storage initiator (usually a server) to send SCSI commands to a storage target (usually a tape or disk) over IP. iSCSI technology provides compelling price/performance in a simplified architecture while improving manageability in virtualized environments.
SCSI protocol is not designed to handle lost frames, or blocks. It expects them to arrive, no matter if they're damaged (have CRC errors). IP or Ethernet will not deliver a frame which has CRC errors; behavior which is not compatible with what SCSI expects. This is why iSCSI uses TCP.
The way to improve performance of iSCSI is to use HBAs (Ethernet NIC) with TCP offload, which do all the necessary calculations on an embedded ASIC, significantly reducing the processing latency. Majority of storage arrays with iSCSI already make use of TCP offload, so some of the performance problems that you're seeing are quite likely caused by a poor choice of Ethernet NIC in the server (or incorrect/badly configured NIC drivers). Broadcom NetXtreme II network adapters can be used for Iscsi Offload.
Specifically, iSCSI offers virtualized environments simplified deployment, comprehensive storage management and data protection functionality, and seamless VM mobility. Dell iSCSI solutions give customers the "Storage Direct" advantage - the ability to seamlessly integrate virtualization into an overall, optimized storage environment.
In Linux you can use iscsiadm command to login the ISCSI targets and allows to discover.In CentOS 5.1 adds over the 5.0 version is an updated iscsi-initiator-utils. It adds the "iface" context, which allows you to configure more than one physical interface for connection to iSCSI targets. With CentOS 5.0 the best alternative for redundant paths was to use the Linux bonding driver and create an active-standby bond between two interfaces. This is great for redundancy, but doesn't provide and load balancing.
Dell's PS Series group provides iSCSI-accessible block storage. With the latest version of the PS Series firmware and the addition of an EqualLogic FS7500, the same PS Series group can provide block storage and support for NAS (Network Attached Storage). FS7500 is integrated directly into the EqualLogic Group Manager to improve productivity, making it easy to configure and manage iSCSI, CIFS and NFS storage.
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