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With Windows 8 Storage Spaces, you can lump many hard disks of varying types, speeds and sizes together to use as a single storage space / logical drive.

How does Windows decide what to place where?

For example will it move files about depending on frequency of access? Maybe splitting files frequently accessed together between hard disks etc.

What does it optimize for? Speed, reliability, etc?

If the above is asking too much, can I easily see where the files are physically (on which physical disk)?

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All we know is what Microsoft tells… – Moab Oct 23 '12 at 15:33
Recovery looks to be a nightmare should anything go… – Moab Oct 23 '12 at 15:33
All the information Microsoft has released on Storage Spaces is public knowlege, outside of that knowlege, this can't be really be answered by anyone except Microsoft. The article doesn't really seem current, has nothing really to say, except when hardware fails data recovery is tough ( this is already true ). – Ramhound Oct 23 '12 at 15:36
As per the Virtualizing storage for scale, resiliency, and efficiency article, "all data is striped across all physical disks backing the space". – Karan Oct 23 '12 at 15:46
@Karan should be an answer. – Moab Oct 23 '12 at 15:58
up vote 3 down vote accepted

There are three different data resiliency options available: two-way mirroring requires at least two physical disks, and will place a copy of each of your files on both drives; three-way mirroring requires at least five disks and will store a copy of each file on three of the five; and "parity" mode requires at least three disks and duplicates your data using less physical space on each disk, but has higher performance overhead—Microsoft recommends that it be used primarily for large files that are rarely changed.

In a storage space with two-way mirroring enabled, a copy of every slab is kept on both disks so that if one goes down, no user data will be lost.



I believe you can view the files

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Try this article. It explains in explicit detail how storage spaces work to optimize speed and recoverability. IT IS NOT JBOD.

To explain here, Storage spaces stripes your data across all applicable drives evenly, filling them up evenly.

If you are working in a Mirror system, all data is replicated exactly with its paired mirror drive. so if you have 2 drive in mirror, 1 and 3 will be identical, and 2 and 4 will be identical.

If you are working in Parity mode, the last drive in the array is flagged as parity and stores all that information. the remaining drives will stripe data across them evenly.

It does not make any optimizations based on file access frequency or medium. Since storage spaces cant be booted to, it assumes that none of the files stored therein are system files and treats all files equally. (this is the same behavior as if you were using a traditional RAID array, so this is NOT a bug.)

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Its RAID-0, or striping. It can be done with mirroring or parity.

How does Windows decide what to place where?
It writes in parallel across all your disks, nothing is going to get written to a single physical disk.

What does it optimize for? Speed, reliability, etc?
It optimizes for speed. It writes the data across all drives in parallel, reducing write speed to x/(number of disks), where x would be the normal write speed to any given file on a single disk.

Can I easily see where the files are physically (on which physical disk)? No, because they are going to exist across all the drives, never on just a single physical disk.

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