Monday, 8 November 2010

Moving drives across ports in a RAID

Can I swap the disks in RAID (connect the disks to different ports) and don't lose the RAID data?

There are two types of RAID implementation:

1. Configuration-on-disks (COD) - in which the information about RAIDs along with the data about to what array exactly the current disk belongs to is stored on the disk itself.
In this case you can transfer the disks between the ports and even between the controllers of the same model. Such a scheme is implemented in modern software RAIDs (Windows LDM and Linux mdadm) and in most hardware controllers as well. Sometimes you can even transfer the array between the different controller models, for example Intel ICH9R and Intel ICH10R.

2. RAID implementations in which the information about member disks is stored in the controller memory. Here, the controller actually monitors not the disks, but the ports and so you cannot swap the disks. Othewise, you lose the array and then you need a RAID recovery.

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