Note: This article is now out of date. While the Apple Xserve RAID is still found in legacy installations, it has been replaced by the Promise RAID for new installations. The most typical storage found in Xsan setups is the Apple XRAID. Any XRAID will work within an Xsan deployment. XRAID systems being used in an Xsan should have the maximum amount of RAM available, which is 512MB. The Apple XRAID comes with 14 drive modules. Drive modules in an XRAID are split into two channels, each with 7 modules. Drive modules are just UltraATA or SATA enclosures for the Hard Drives used in an XRAID. XRAIDs are available in…
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Xsan: cvgather
cvgather is a command in Xsan, located in the /Library/FileSystems/Xsan/bin folder that allows you to “gather”up all the relevant configuration information for your Xsan environment and save them into a compressed file. Use it, love it, even script around it as it could get you out of some serious issues if you find yourself in them.
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The Anatomy of a RAID
Originally posted at http://www.318.com/TechJournal The acronym for RAID can often be misleading as it has had multiple meanings over the years. RAID originally stood for a redundant array of inexpensive disks. The acronym RAID is now also known as a redundant array of independent disks as not all RAID disks are inexpensive. RAID refers to a hard drive storage mechanism using multiple hard drives to share or replicate data among the drives. In some cases this can mean having data that is written to a single logical drive stored on multiple drives so there is redundancy of the data or RAID can be used to maximize throughput to drives by…
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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…
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Xsan: Qlogic Licensing
In order to stack Qlogic switches all 20 ports must be active. Not all ports are active on all switches. Good to know… THIS POSTING IS OUT OF DATE
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Xsan: Metadata Network
Xsan needs an out-of-band metadata network. This network is used to transfer information, or metadata on files being written to the SAN. The metadata network on an Xsan should be low latency. Nothing should potentially interfere with the transfer of data. Therefore, make sure that you disable all the management features of your switch. But make sure it’s a good switch. I prefer to use a managed switch, disabling all the management features.