Earlier, we described a LUN. In Xsan you can take multiple LUNs and stream data to them in a round-robin fashion. When doing so you will group them together in what Xsan calls Storage Pools. Each Storage Pool has a maximum throughput of about 4 LUNs worth of storage. Each of the LUNs (in Xsan 1.0) has a maximum of about 2TB in capacity. Therefore each Storage Pool can typically net you around 4gbps of speed and about 8TB in capacity. You can then lump multiple Storage Pools into a given Volume to obtain volume sizes of 32, 40, 48, etc. TB. However, when you do so you will not…
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Installing Xsan 1.x
You will install the xSAN software on all of the systems that will be running as Metadata Controllers and on all of the client computers. To install the xSAN software: Run the Install Xsan.mpkg file from the Xsan Install Disc. Read the Welcome to the Xsan Installer screen and click Continue. Read the Important Information and click Continue. Read the Software License Agreement and click Continue. Agree to the Software License Agreement by clicking on the Agree button. Select the volume for the Xsan software to be installed on. Once your Destination has been selected, click Continue (see Figure 2.x). Figure 2.x Select a Destination If you would like to…
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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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Xsan: What is Fiber Channel
Fiber Channel is a technology for transmitting data between computer devices similar to SCSI but with networking components based on fiber optics. Fiber Channel is especially suited for attaching computer servers to shared storage devices and for interconnecting storage controllers and drives. Apple uses Fiber Channel for Xsan, it’s storage virtualization platform. All of the objects that make up a Fiber Channel network are referred to as the fabric. These typically include HBAs (the card that goes in a machine), cabling, transceivers, a fiber channel switch and the fiber channel controllers on the storage.
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Xsan: Reset Qlogic Password
Lost the password for your Qlogic? You can TFTP a new firmware file into a 5xxx switch and then do a factory reset while it’s in maintenance mode (follow the instruction exactly as they are in the latest version of the manual for your switch). Or if you have a serial adapter you can break the boot sequence by using the space bar during boot. At the prompt use: factory 1 If you factory reset it then the default IP address will be 10.0.0.1 again and the default password will be back to password. If you have the password and just want to reset it back to factory defaults then you…
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Rebuilding Arrays on Xserve RAIDs
Sometimes a drive fails, or a RAID controller goes down on an array with a redundant drive (eg – RAID 5 or RAID 3) and the parity on a RAID must be rebuilt. This should happen as quickly as possible. However, it can result in data loss and in the event of a second drive failure on the array most of the data could be lost. The data may be safe, and should be backed up as quickly as possible. Once the data is backed up, then you should perform a rebuild of the parity for the array. To do so open RAID Admin from /Applications/Server and click on the…
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Xserve RAID: Reset Controller
Unmount any Xserve RAID volumes hosted by the RAID (especially Xsan volumes). Press the reset button on the back of the controller module for about ten seconds. You should see the controller restart and then the controller should be reset. Sometimes you need to reset both controllers. You don’t have to reset the whole controller to just reset the password. To do that, you can press the reset button for about 1-2 seconds and then try to authenticate through RAID Admin to reset the password. By default the password to view the Xserve RAID, once reset is public and to edit settings, the default password is private. By default the IP…
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Planning For Xsan
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…