Mis-Design of Btrfs?

From: Nico Schottelius
Date: Thu Jun 23 2011 - 07:02:40 EST

Good morning devs,

I'm wondering whether the raid- and volume-management-builtin of btrfs is
actually a sane idea or not.
Currently we do have md/device-mapper support for raid
already, btrfs lacks raid5 support and re-implements stuff that
has already been done.

I'm aware of the fact that it is very useful to know on which devices
we are in a filesystem. But I'm wondering, whether it wouldn't be
smarter to generalise the information exposure through the VFS layer
instead of replicating functionality:

Physical: USB-HD SSD USB-Flash | Exposes information to
Raid: Raid1, Raid5, Raid10, etc. | higher levels
Crypto: Luks |
LVM: Groups/Volumes |
FS: xfs/jfs/reiser/ext3 v

Thus a filesystem like ext3 could be aware that it is running
on a USB HD, enable -o sync be default or have the filesystem
to rewrite blocks when running on crypto or optimise for an SSD, ...



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