nothing is impossible!!!!

nothing is impossible!!!!

Sunday, February 7, 2010

SAN terminologies

Here I am trying to put every definition related to SAN on single page. Its a collective information from different sites.

AoE: ATA over Ethernet: its a network protocol designed to access SATA storage devices over the Ethernet networks. AoE does not rely on network layers above Ethernet, such as IP and TCP.
The advantage of AoE is that you don't have the overhead of translating ATA to SCSI and then back to ATA (if you are using ATA drives). So there is a performance pickup.

NBD: The Linux Network Block Device (NBD) is a device driver extension to the Linux kernel. With the NBD device driver you can create a TCP/IP network connection between your local Linux system and a server program on a remote (not necessarily Linux) computer. But NBD has some limitations in terms of read/write operation and using NBD as a root file system.
Server processing load for iSCSI is much higher than AoE for equivalent throughput. AoE can spare processing cycles. iSCSI requires TCP/IP and its requisite complexity.

ENBD- Enhanced Network Block Device
GNBD- Global Network Block Device

WWPN: World Wide Port Name. A globally unique identifier for a port which allows certain applications to access the port. The FC switches discover the WWPN of a device or host and assign a port address to the device.

Multipathing: When transferring data between the host server and storage, the SAN uses a multipathing technique. Multipathing allows you to have more than one physical path from the Server host to a LUN on a storage array.
If a default path or any component along the path—HBA, cable, switch port, or storage processor—fails, the server selects another of the available paths. The process of detecting a failed path and switching to another is called path failover.

An active/active disk array, which allows access to the LUNs simultaneously through all the storage processors that are available without significant performance degradation. All the paths are active at all times (unless a path fails).

An active/passive disk array, in which one SP is actively servicing a given LUN. The other SP acts as backup for the LUN and may be actively servicing other LUN I/O. I/O can be sent only to an active processor. If the primary storage processor fails, one of the secondary storage processors becomes active, either automatically or through administrator intervention.

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