Messages in this thread | | | Subject | Re: Notes on support for multiple devices for a single filesystem | From | Chris Mason <> | Date | Wed, 17 Dec 2008 16:41:58 -0500 |
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On Wed, 2008-12-17 at 14:24 -0700, Andreas Dilger wrote:
> I can't speak for btrfs, but I don't think multiple device access from > the filesystem is a "layering violation" as some people comment. It > is > just a different type of layering. With ZFS there is a distinct layer > that is handling the allocation, redundancy, and transactions (SPA, > DMU) > that is exporting an object interface, and the filesystem (ZPL, or > future > versions of Lustre) is built on top of that object interface.
Clean interfaces aren't really my best talent, but btrfs also layers this out. logical->physical mappings happen in a centralized function, and all of the on disk structures use logical block numbers.
The only exception to that rule is the superblock offsets on the device.
-chris
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