Example if you wanted to define a 100 gigabyte

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example, if you wanted to define a 100 gigabyte storage space and you used two-way mirroring to provide resiliency, we would have to install 200 gigabytes of physical disk space in the system. By way of comparison, if we wanted to define the same 100 gigabyte storage space using parity in the system,we would only have to have about 150 gigabytes of physical disk space. 256 MB Chunks of Data 6:13-6:53 All of the different resiliency strategies that we've talked about, two-way mirroring, three-way mirroring, and parity, will store data on the drives in 256 megabyte chunks. Now, suppose we have a storage space that's configured using two-way mirroring. In this situation, a redundant copy of each 256 megabyte chunk is stored on both disks in the storage space so that if one of the disks goes down, no user data with be lost. It's still available on the second disk. If you add new disks to the pool,the original disk from the pool will fill up that new disk with all of the different 256 megabyte chunks that it has in order to push the redundancy over onto the new disk installed in the system. Resiliency is Preserved 6:54-7:19 The key thing to remember is that adding new disks to the pool does not affect the resiliency. All the information is copied over to the new disk so that resiliency is preserved, and that's really nice because if one of the original disks on a system dies, that redundant information is already copied over to any new disk you add to the pool. And the process for doing this is easy enough that most end users can handle it without a lot of training. Thin Provisioning 7:20-9:11 Another key benefit provided by Storage Spaces is thin provisioning. Sometimes, it's called overbooking. The idea here is that when you create a new storage space, you can actually set the size of that storage space to a value that's actually bigger than the amount of physical storage space in the pool. It does this by thin provisioning, meaning that if we assign a size to one particular storage space like this one, the physical storage is not really assigned to that storage space. For example, let's suppose that I have 10 different users who use the same system and I want toallocate 100 gigabytes of storage space for each of them, like these here. Your first inclination might be to say, "Well, I want to define a storage space of 100 gigabytes per user, and there are 10 users. Therefore, I'm going to need a storage pool that is one terabyte in size, right?"Not necessarily because we know, in all likelihood, that not all of those users are going to consume all of their 100 gigabytes of storage space. In fact, most likely, they're only going to consume a fraction of that space. Some users will use all 100 gigabytes, some of the users will not. Therefore, Storage Spaces actually allows us to create multiple storage spaces whose sum total size is larger than the storage pool itself. In this example, we can create 10 100 gigabyte storage spacesfrom a 500 gigabyte storage pool.
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  • Spring '14
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