Make the most of zoning
Rick Cook
Zoning is a fundamental technique for SAN management that can be implemented several different ways. In all cases zoning serves to limit users' access to the appropriate storage devices. This increases security and decreases traffic over the network.
Storage resources are usually zoned either at the device level or the LUN level. In device-level zoning each user is restricted to accessing specific physical devices such as RAID arrays or individual disks. Zoning at the LUN level allows the administrator to allocate space in logical units rather than physical chunks. A LUN zone may be spread over several physical devices, often sharing the devices (but not the storage space) with several other zones.
Zoning is a powerful tool for making the most efficient use of storage assets in a SAN. But it must be planned carefully to make the best use of the available storage and the network's bandwidth. Zoning usually makes it harder to shift storage capacity from one group of users (in one zone) to another and making such a switch without rebooting can create security holes since users in both zones may end up with access to the storage space which has been moved.
LUN zoning has usually been implemented in the physical devices or their controllers. However some SAN makers now offer LUN zoning implemented through the switch.
JNI offers some information about LUN zoning at its web site (www.jni.com).
Brocade discusses its version of switch-level LUN zoning in a white paper at:
http://www.brocade.com/SAN/white_papers/pdf/IncreasingIntelligenceWithinSAN.pdf.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
Additional Resources:
- What's the difference between LUN zoning and WWN zoning? One reader asked SAN expert Christopher Poelker about any security issues with respect to SAN environments. Chris responded by first explaining the security benefits of all I/O occurring over optical fibre. He then went on to clearly describe the different types of zoning in a SAN and how they relate to LUN security.
- How does virtualization software affect zoning? Jon Toigo was recently asked how a Microsoft operating system and Microsoft servers handled dynamic allocation of SAN-related storage. Jon tapped the folks at Datacore Software for an interesting answer on how the company's own virtualization engine handles LUN zoning and dynamic allocation of storage in Microsoft environments.
- How do I eliminate switch zoning at the fabric level? Here's another good question (and answer) on partitioning data sets within a SAN. Expert Chris Poelker provides more input on WWN zoning and ways to elminate the need for switch zoning at the fabric level.
- How do I migrate storage from one vendor array to another? (Answer: Part I, Part II) Expert Christopher Poelker has outdone himself with this detailed, two-part answer to a recent question about the best practices for transferring storage from a Compaq StorageWorks device to an EMC Symmetrix. His procedure assumes that the LUNs are preconfigured in the new array and set to the same size and RAID type as the old array. He also mentions that any SAN zoning has to take into account the new WWN of the HBA used for the move. Part II contains 15 detailed migration steps to follow.
- In our forums: Where is EMC with virtualization/LUN zoning? Several posters have been having a lively debate in our Storage Networking discussion forum. They've been arguing the merits of virtualization, their ratings of current "virtualization" vendors, abstraction layers, and what EMC's products and others can/cannot do in the area of LUN zoning and other areas. If you are interested in this subject, feel free to add your voice to the debate. We suggest you read back through the most recent threads.
- Do you have zoning questions? Ask an Expert! Submit your questions on zoning and other SAN issues to our Storage Networking experts.
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