Re: Volume Managers in Linux

Andi Kleen (ak@muc.de)
04 Nov 1998 18:43:20 +0100

In article <19981103214553.D12914@nodonn.cloud9.co.uk>,
James Fidell <james@cloud9.co.uk> writes:
> Quoting Theodore Y. Ts'o (tytso@MIT.EDU):
>> I've never claimed that the ext2 is the best way to do RAID; I think MD
>> is the way to do that. However, allowing ext2 to be able to support
>> filesystems which span multiple block devices is a good thing to do, and
>> a cleaner way of supporting multivolume support. Examples of
>> filesystems which do this include the UDF filesystem used by DVD-ROM's,
>> and Digital Unix's Advanced Filesystem.

> What "feels wrong" about this to me is that all fs implementations are
> then required to implement multiple device spanning, or they can't be
> used on spanning partitions at all.

Linux already has MD which does RAID 0 (= device spanning) just fine for
all filesystems who want it. Now the big problem is to allow
shrinking/increasing such bundles without recreating the file system -
only the file system itself knows enough about its structure to offer
this service, no generic layer can provide that.

-Andi

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