To reset RAID Controllers on an Xserve RAID: Reset the NVRAM to return the XRAID to factory default settings by holding down the reset button on the back of the controller for 5 seconds and then releasing the button. If you need to reset both controllers, you should reset the lower controller first and then reset the upper controller. The Xserve RAID will now have the name Xserve-RAID and an automatic IP address. The location and contact information are also reset. The settings for drives, drive cache, prefetch and other array based information will not be reset. If you only want to reset the password of an Xserve RAID you…
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Xsan: Backing up the Configuration
cvgather is a tool that can be used to “gather” up all the relevant information (cfg files, etc) on your Xsan and back them up to a specified location. Any time you will be fussing around with the SAN, etc. then you should run this first. Additionally the copy of the config files can provide you with an escape clause with regard to certain issues that could cause the volume to get destroyed so I would have a copy of all your info on a location other than the SAN at all times anyway. This isn’t to say that cvgather will actually back the SAN itself up. It very specifically…
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Mounting a Volume for Xsan 1.x
To mount a volume: Open xSAN Admin from /Applications/Server. Under the SAN Components list click on the Volume you would like to mount. Click on the Clients tab for the volume. Click on the client you would like to mount the volume for (see Figure 2.x). Click on the Mount Read Only if the client system does not need to write to the volume. If the client system does need to write to the volume, click on the Mount Read Write button. Figure 2.x Mounting the Volume on a client Once you have mounted the volume, click on it using the Finder. Click on the Finder menu of the system…
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Xsan: Corruption
Volumes can become corrupt no matter what file system you are talking about (er, there might a magical file system out there that cannot become corrupted but I’ve never heard of it and would like to sell a certain bridge to you if you have). Xsan is no different and so you need to be ready to use the command line to combat said corruption. fsck is the traditional *nix tool to fix issues with volume corruption. cvfsck is the weird cousin that’s used for Xsan. If you see any iNode errors in your logs, corruption errors, high latency or just too many weird issues to shake a stick at…
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LinuxWorld Toronto
Details of the talk I’ll be giving at the upcoming LinuxWorld in Toronto, Canada: http://www.lwnwexpo.plumcom.ca/session_detail.cfm?id=239
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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: Fragmentation
Xsan volumes can get fragmented. This can cause the performance to move to a grinding halt. Dropped frames, slow copy times, even volume corruption are common side effects. So, to defrag the volume you can use snfsdefrag. This command-line tool will defrag volumes or files. You can even specify what to do with the fragmented data, giving you a way to move data between storage pools…
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Uninstalling Xsan
When the standard troubleshooting steps do not work for an xSAN client it is sometimes a good idea to just uninstall the software and reinstall it. You also may decide to repurpose an aging system out of the xSAN. To uninstall xSAN from a system: Open xSAN Admin from /Applications/Server Unmount all of the volumes for the system you are uninstalling. Backup the /Library/Filesystems/Xsan/config directory for the system. Open the Uninstall Xsan.pkg file from the CD or other location it is available at. At the Welcome ot the Xsan Uninstaller Installer screen click continue. At the Select a Destination for Uninstall screen, click on the volume you want to uninstall…
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Xsan: Multiple Volumes
In Xsan 1.x you can have multiple volumes. Each will consist of a given number of Storage Groups that in turn consist of a given number of LUNs, as we’ve described in the past. If you have multiple volumes then they will all use the same Metadata Controllers. Each additional volume will also need its own dedicated Metadata LUN. Therefore, if you have 4 volumes, with 4 LUNs of data storage in each volume then you will have a total of 16 LUNs for data and another 4 for metadata to total out 20 LUNs. Essentially by splitting it up this way you are loosing 4 LUNs (up to 20TB…
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Xsan: Affinity
cvaffinity can be used to assign an affinity to a storage pool in Xsan. An affinity maps a specified directory to a storage pool. Therefore, if you have a dedicated capture station and you want to make sure it always has 4gbps of throughput then you can create a storage pool called capture, mark it for use with affinity only, create a folder called capture and assign the affinity for the capture storage pool to the capture folder on the volume. Now all data written to that folder will be written through the affinity and therefore provide a certain level of Quality of Service to that affinity.