![]() Both in terms of performance and capacity. It kind of goes without saying, but I will say it anyway – only add drives that match the same capability as those already in the DRAID array. Stick to a rough rule of 1 spare per 24 drives. New drives can be used to increase the number of spare areas. Up to four expansions can run in parallel on a single system, assuming you have four or more pools., i.e. In addition, only one expansion is permitted per storage pool at any point in time. Only one expansion task can be in progress on a given DRAID array at any point in time. If you need to add more than 12 drives to a DRAID array, this would involve multiple serialised tasks. That is, you can decide to expand in multiples of up to 12 drives. What can be added?īetween 1 and 12 drives can be added in a single operation or task. New drives are integrated and data is re-striped to maintain the algorithm placement of strips across the existing and new components.Įach stripe is handled in turn, that is, the data in the existing stripe is re-distributed to ensure the DRAID protection across the new larger set of component drives.Īll pools and volumes remain online and available during the expansion. you can do this and continue to access the data on the DRAID array. The expansion process is dynamic, and non-distruptive, i.e. ![]() The number of distributed spare strips that are available for each stripeĭRAID Expansion provides the ability for you to dynamically add one or more drives and increase the component count of an existing in use DRAID array. The chosen protection and stripe width, i.e. The count of strips that make up a stripe So in summary the terms we will use are : component countĪ chunk (256KB) of capacity on a single driveĪ set of strips that make up a single instance of the chosen geometry In reality the 7+P stripe would appear to be dispersed randomly across 8 of the 24 drives for each stripe! Please note that the actual algorithmic layout is not represented, this is just for simple illustration of the terms used. In this example slide the component count is 24, the geometry is 7+P and there is 1 spare area. Additionally, between 1 and 4 spare areas can be configured per DRAID array. The stripe width being the n+P+Q, which will always be lower than the component count. Each drive provides a strip that makes up a stripe. The geometry being the normal n+P+Q layout. DRAID BasicsĬheck out the DRAID – How it Works post for more details but in summary a DRAID array is made up of a given number of component drives (often called a pack or row) which is usually larger than the RAID geometry. Before we dive in, there are some DRAID basic terms that you need to understand. When I introduced the updates in Spectrum Virtualize 8.3.1 I promised a dedicated post discussing the details around the new DRAID dynamic expansion feature.
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