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Windows 10 Storage Spaces: Two-way mirror vs. parity?

hanime 737 156 February 20, 2016 at 04:24 PM
I've been reading between the two and I'm still confused about how they work within Windows 10 Storage Spaces. Two-way mirror "writes data to either two disk or three disks simultaneously, so that you have multiple copies of your data (Like a RAID 1)" while parity "stripes data across the disks in the pool (like a RAID 5)". Both appears to be able to survive a single disk failure, but parity is slower than two-way in writes.

I have 3 x 5TB drives in which I want to have resiliency, and then add more drives when necessary in the future. Normally I would think two-way mirror works with two drives, but there seems to be an option for three or more drives. How does that work with odd quantity and size of drives? Given the two options, which should I go with, two-way mirror or parity?

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#2
Quote from hanime View Post :
I've been reading between the two and I'm still confused about how they work within Windows 10 Storage Spaces. Two-way mirror "writes data to either two disk or three disks simultaneously, so that you have multiple copies of your data (Like a RAID 1)" while parity "stripes data across the disks in the pool (like a RAID 5)". Both appears to be able to survive a single disk failure, but parity is slower than two-way in writes.

I have 3 x 5TB drives in which I want to have resiliency, and then add more drives when necessary in the future. Normally I would think two-way mirror works with two drives, but there seems to be an option for three or more drives. How does that work with odd quantity and size of drives? Given the two options, which should I go with, two-way mirror or parity?
For 2-way mirroring (~RAID1), it just makes sure that your data is written to at least 2 drives, similar to what btrfs does in Linux. Your data is written twice, so half your disk space is usable.

With parity (~RAID5), it writes your data once to N-1 drives, and writes parity data to the Nth drive. You only have one disk storing redundant data, so you get all the storage space of the remaining drives.

RAID5 failures (if more than one drive fails at once or during recovery) tend to be a bit more catastrophic than RAID1 failures, but you can use more of your space.

The decision is really up to you. Depends on how important the data is, whether you have offsite backups, etc....
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#3
Thanks for the response. I'm giving the 2-way mirroring a try on the 3 drives. Since it's a 3-drive setup, what would be the usable disk space?
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#4
Quote from hanime View Post :
Thanks for the response. I'm giving the 2-way mirroring a try on the 3 drives. Since it's a 3-drive setup, what would be the usable disk space?
3x5TB with 2-way should give you 7.5TB of usable space.
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