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lvm plus raid10? Why? LVM will provide the functional equivalent of the raid0 part of a conventional raid10 instance, but with much more functionality and flexibility. Additionally, LVM can perform mirroring internally, so you can take 4 drives and merge them into one large logical device, with half the total capacity on the drives, with at least 1 spare copy of all data. Sounds like raid10 to be, but with knobs on when you also take 20% of that total capacity for snapshot space too. No Jacket, erm... RAID required.
the lvm mirroring code is rather new, compared to that of md, isn't it?
is it stable for production use?
LVM will provide the functional equivalent of the raid0 part of a conventional raid10 instance, but with much more functionality and flexibility. Additionally, LVM can perform mirroring internally, so you can take 4 drives and merge them into one large logical device, with half the total capacity on the drives, with at least 1 spare copy of all data. Sounds like raid10 to be, but with knobs on when you also take 20% of that total capacity for snapshot space too. No Jacket, erm... RAID required.
does the size of the logical volumne need to be smaller than the available capacity in order to use snapshotting?
does the lvm handle disk failures just as well as a linux software raid?
probably I need to do some benchmarks, when the hardware arrived.
To be honest I've not used mirroring on LVM so have not had to recover one, but the reference there is clearly about raid 1 + LVM, not raid 10 + LVM, which was mainly what I was replying about, and would really avoid. raid1 + LVM, well fine, do what you're comfortable with there...
In terms of access performance, i *believe* that with the correct stride size on LVM you can write data fast across your disks. Conversely, with a bad choice of stride size you can theoretically reduce your performance.
In terms of snapshot size, yes you need to reserve space. The way it works is that when you trigger a snapshot, all further changes are done to the spare space, with a different version of the inode tree being maintained. Original data, and unchanged data, remains exactly where it is, with an older version of the inode table pointing to the data which constitues the preserved data. When the snapshot space runs out, then the old space has to be used, and at that point the old data has to be reused and the snapshot becomes invalid. Kinda neat, huh?