Re: [patch] pagecache-2.3.9-H3, bmap & ext2fs cleanup patch

Matti Aarnio (matti.aarnio@sonera.fi)
Sun, 27 Jun 1999 17:07:40 +0300

On Sun, Jun 27, 1999 at 03:37:28PM +0200, Ingo Molnar wrote:
> On Sun, 27 Jun 1999, Andrea Arcangeli wrote:
> > BTW, I think that a filesystem that span over multiple devices could make
> > better choices than raid, right?
>
> no, RAID is really a different concept, and it's filesystem independent.
> multi-device filesystems _might_ be useful but the cleanest way of
> handling striping and/or redundancy is IMO MD at the block device layer.
> Caching and block allocation decisions are best done on the filesystem
> level.

Right. They are orthogonal issues.

However do remember that our current blockdevice level limitation
is 2G (or 4G ?) worth of 512 byte blocks, that is, 1 TB (maybe 2)
for any given block device size.

Your filesystem can't grow over that if you are limited to single
blockdevice per filesystem.

All that RAID supplies for a filesystem is single block device,
however large/redundant/etc. that might be.

I am inclined to think that what we need out of the future file-
systems is much more in multi-device spanning style, than any
RAID/LVM/MD creation.

> -- mingo

/Matti Aarnio <matti.aarnio@sonera.fi>

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