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On Sat, Feb 25, 2012 at 4:56 PM, Richard Yao <ryao@×××××××××××××.edu> wrote: |
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> raidz has 3 varieties, which are single parity, double parity and |
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> triple parity. As for reshaping, ZFS is a logical volume manager. You |
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> can set and resize limits on ZFS datasets as you please. |
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That isn't my understanding as far as raidz reshaping goes. You can |
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create raidz's and add them to a zpool. You can add individual |
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drives/partitions to zpools. You can remove any of these from a zpool |
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at any time and have it move data into other storage areas. However, |
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you can't reshape a raidz. |
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Suppose I have a system with 5x1TB hard drives. They're merged into a |
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single raidz with single-parity, so I have 4TB of space. I want to |
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add one 1TB drive to the array and have 5TB of single-parity storage. |
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As far as I'm aware you can't do that with raidz. What you could do |
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is set up some other 4TB storage area (raidz or otherwise), remove the |
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original raidz, recycle those drives into the new raidz, and then move |
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the data back onto it. However, doing this requires 4TB of storage |
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space. With mdadm you could do this online without the need for |
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additional space as a holding area. |
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ZFS is obviously a capable filesystem, but unless Oracle re-licenses |
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it we'll never see it take off on Linux. For good or bad everybody |
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seems to like the monolithic kernel. Btrfs obviously has a ways to go |
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before it is a viable replacement, but I doubt Oracle would be sinking |
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so much money into it if they intended to ever re-license ZFS. |
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Rich |
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