The Promise Vtrak is the only officially supported platform that can be used to provide LUNs to an Xsan. Having said that, there are a number of other storage vendors that are supplying LUNs at this point. And while I don’t really want to speak to that it is worth noting that it brings me joy to watch the ever-expanding number of vendors testing their products for and then marketing to the Xsan community. One that I came across recently is Dot Hill, who did a video showcasing their speedy 2U product at NAB.
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Xsanity: Using Removable Media with Xsan
I posted another article on Xsanity. This one started out as an article on how to label LUNs from the command line, but ended up something completely different. It still explains how to do it from the command line, but since I wrote it while flying it ended up being more tailored to doing it on a USB jump drive since they don’t allow me to take an Xserve, Qlogic 9200 and a Promise RAID to my seat on the plane with me. Which is really a shame ’cause I could get SOOOO much done that way. Anyway, the article can be found here.
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How to Use Xsan with iSCSI
Using iSCSI targets with Xsan… Don’t do this one at home kids. It’s just silly and not going to be supported by anyone… But if you are like me then you can do it if you must. So to get started with iSCSI check out this article. When you have a LUN that is connected don’t yet assign it a file system (or if you have partition it back to free space). Now install Xsan but don’t yet create a volume. Once you’re done, you can go ahead and fire up your trusty Terminal app from /Applications/Utilities. Type in cvlabel -l which should show you all your available LUNs. Next,…
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LUNscaping
In Xsan you need to plan your LUNs carefully. I’ve decided to call this process LUNscaping. Join me with this and feel free to take credit for the term… 😉
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Xsan: Speed and Capacity
When a LUN, Storage Pool and/or Volume gets too full then the SAN is going to get slower. It’s also going to become more prone to data corruption as it cannot find locations to place files quickly enough. So be kind to your SAN and always make sure you have plenty of space available.
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Xsan: Zoning and Metadata
Only the MDCs are required to see the Metadata LUN. The rest of the clients receive the extents from the MDCs to write to the “data” LUNs. Yes the clients need to see the Data LUNs, but clients do not need to see Metadata LUNs. Before you can upgrade a client to an MDC though, verify that you can see the Metadata LUNs if you are zoning this way. It’s the most secure way but requires a little extra zoning.
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Xsan: LUN
An Xserve RAID can be split into multiple logical units, referred to as a LUN. Each side, or channel, of the RAID is, by default a single LUN. You can use the RAID Admin utility (located at /Applications/Server) to format each of these as multiple LUNs if you wish. When the LUNs are formatting (which generally takes 48 hours) you will start to see them in disk utility. Do not assign a file system to them yet if you are to use them with Xsan. Instead you will use the cvlabel command to label each of your LUNs, which marks them as able to be used by Xsan.
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Zone Defined
A zone in Fibre Channel is a segment of a fabric that is composed of selected targets and initiators. Like with a VLAN, only the members of a zone have access to one another. Simply because the switch allows the members to access one another doesn’t mean you can’t still limit access more granularly. You can use storage-based filters, such as LUN Masking, for which devices can access one another based on WWNN information from the initiator port. With Xsan, you can use LUN Masking to limit which of the hosts on your SAN have access to your Xserve RAIDs. UPDATE: LUN Masking was removed as a feature from the Xserve…