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'''Host-based zoning''' can include [[World Wide Name|WWN]] or [[Logical Unit Number Masking|LUN masking]], and is typically known as '''“persistent binding.”'''<br />
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In [[storage networking]], '''”persistent binding”''' is an option of [[Fibre Channel zoning|zoning]].<br />
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Host-based zoning is usually referred to as persistent binding or LUN,<ref>mapping</ref> and is perhaps the least implemented form of zoning. Because it requires the host configuration to be correct in order to avoid zoning conflicts, this form of zoning creates a greater opportunity for administrative errors and conflicting access to targets. Moreover, zoning interfaces vary among different host [[operating system]]s and [[Host adapter|HBA]]'s — increasing the possibility for administrative errors. If a host is not configured with the zoning software, it can access all devices in the fabric and create an even higher probability of data corruption. Host-based zoning is often used when clusters are implemented to control the mapping of devices to specific<ref>SCSI</ref> target IDs. However, it should never be the only form of zoning. Augmenting host-based zoning with storage- and fabric-based zoning is the only acceptable method to reliably control device access and [[data security]].<br />
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Basically, A given [[Logical Unit Number|LUN]] has it [[SCSI]] id assigned by its [[Disk array controller|RAID device]] (typically a [[Storage area network|SAN]] ). But for some purposes it's useful to have the SCSI id assigned by the host itself: that's '''persistent binding'''.<br />
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==What is Persistent binding for ?==<br />
Without persistent binding, after every reboot, the SCSI id of a LUN may change. For Example, under [[Linux]], a LUN bound on /dev/sda could migrate to /dev/sdb after a reboot. The risks augments with [[Multipath I/O|multipathing]]. Based on that, it is obvious that many software may crash without persistent binding.<br />
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from http://www.storagesearch.com/datalink-art1.html<br />
:''Operating systems and upper-level applications (such as backup software) typically require a static or predictable SCSI target ID for their storage reliability and persistent binding affords that happening.''<br />
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==Types of zoning==<br />
A zone can include host and LUNS. The LUNS are exported by the DISK ARRAY, the hosts are the clients (servers, [[computers]]). Each host in a zone can access each LUNS in the same zone. That's zoning. The zone is usually set on the central point of connection of the hosts and the DISK ARRAY: the [[Fibre Channel switch|FC switch]].<br />
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==LUN masking==<br />
from [[Fibre Channel zoning]]<br />
:''Zoning is sometimes confused with '''LUN''' masking, because it serves the same goals. LUN masking, however, works on Fibre channel level 4 (i.e. on SCSI level), while zoning works on level 2. This allows zoning to be implemented on switches, whereas LUN masking is performed on endpoint devices - host adapters or disk array controllers.''<br />
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Some fibre channel switches allow zoning at the LUN level, effectively implementing LUN masking at the switch.<br />
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Here, we are talking about level 4.<br />
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This form of zoning has to be augmented by another zoning : [[RAID|RAID ARRAY]] based or fabric-based(FC switch) to improve security and avoid any errors. Otherwise two hosts may access the same data(LUNS) at the same time and it will result in [[data corruption]].<br />
Persistent binding is often used in a cluster environment, to associate a LUN with a persistent SCSI id and device (example /dev/sda)<br />
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==References==<br />
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==External links==<br />
* http://www.storagesearch.com/datalink-art1.html<br />
* http://www.enterprisestorageforum.com/sans/features/print.php/11188_1431341_2 {{Webarchive|url=https://web.archive.org/web/20110710193927/http://www.enterprisestorageforum.com/sans/features/print.php/11188_1431341_2 |date=2011-07-10 }}<br />
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[[Category:Storage area networks]]<br />
[[Category:SCSI]]<br />
[[Category:Fibre Channel]]<br />
[[Category:Computer storage buses]]</div>imported>Widefox