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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StorNext Support for Xsan
The following link shows the compatibility matrix for StorNext Xsan support: http://support.apple.com/kb/HT1517
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Will Any Old GBIC Work?
You have two switches and you’re thinking that you’ll use the GBIC from your old switch on you new switch. You have an Xsan and you have a bunch of GBICs laying around and you want to know if they’ll work. You have a fiber run and you want to use a transceiver. Etc. This is a tricky question. The GBICs should all work. The general rule of thumb though is, if you use the same GBIC on both ends then you shouldn’t have a problem. But, it’s also important that (for whatever reason) some manufacturers do require certain GBICs either to actually interface or just to support an interface.
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Xsan: Designing an Xsan
Planning an Xsan is perhaps the most complicated part of any deployment. First, start with one of two objectives, speed or size (or both). How big does the SAN need to be and what speeds does the SAN (aggregate speed of all clients) need to be able sustain? That becomes the primary design consideration. Beyond that, you’ll also want to plan how it will get backed up and when, the makeup of the clients (Mac, PC, Linux), how permissions will get handled for new files written to the SAN, etc.
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Xsan: Block Sizes
All volumes have a block size. In Mac OS X you can see a block size by entering the following command (assuming disk0): sudo diskutil information 0 If you notice in the Total Size: field you’ll see the number of blocks followed by a block size. By default it is 512 bytes. One of the things that makes it possible to attain high performance from an Xsan volume is the ability for the block size to be customized. The general rule of thumb is that the Stripe Breadth and the Block size should multiply to equal 1MB. So if you have a block size of 256 then your stripe breadth…
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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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Dealing with Drive Failures with Xsan
I originally posted this at http://www.318.com/TechJournal Sometimes a drive fails, or a RAID controller goes down on an array with a redundant drive and the parity on a RAID must be rebuilt. In other words, if you loose a drive in a RAID 5, RAID 1, RAID 0+1 or RAID 3 array you will be left with a degraded RAID (also referred to as a critical RAID) unless you have configured your Xserve RAID to use a hot spare. If you are using a hot spare on the channel of the failed drive the RAID will begin to rebuild itself automatically. If you are not using a hot spare, upgrading…
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Primordial Storage
Primordial storage refers to unallocated storage capacity on a storage device. Storage capacity can be allocated from primordial pools to create storage pools. This means that primordial pools are disk/device sources for allocation of storage pools. In Xsan primordial pools aren’t used but there is often unused capacity in the form of LUNs that are referred to as primordial at time. Especially on a Promise RAID where you might have certain LUNs that are smaller than the potential size of others and therefore might end up with disks left over which can be mapped and used as near-line storage later. This term, primordial, can be used to refer to those.
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Article on EMC Channel Manager Retiring
Another article on EMC I was quoted in: http://www.crn.com/storage/197006487?pgno=2
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AFP, Xsan, Failover & Tokens
When an AFP connection moves to idle, a token is used to establish a reconnect. By default, AFP stores tokens in the local /etc/AFP.conf. But in order to have users reconnect if they move between servers, as in a failoverd event or even in a more active/active relationship with a load balancer you need to move the shared cache to a shared location. To do so you’ll edit the /Library/Preferences/com.apple.AppleFileServer.plist file using the defaults command. The key that you’ll need to change is the reconnectKeyLocation, specifying the string in the key that corresponds to the path to the local server that is running afp to the volume. Therefore, if the…