David Dyer-Bennet wrote:
On 9/11/06, Matthew Ahrens <[EMAIL PROTECTED]> wrote:
Here is a proposal for a new 'copies' property which would allow
different levels of replication for different filesystems.
Your comments are appreciated!
I've read the proposal, and followed the discussion so far. I have to
say that I don't see any particular need for this feature.
Possibly there is a need for a different feature, in which the entire
control of redundancy is moved away from the pool level and to the
file or filesystem level. I definitely see the attraction of being
able to specify by file and directory different degrees of reliability
needed. However, the details of the feature actually proposed don't
seem to satisfy the need for extra reliability at the level that
drives people to employ redundancy; it doesn't provide a guaranty.
I think this is easy to solve and could make such feature more useful -
we need a way to specify policy of placing duplicate copies, e.g. if we
want a guarantee we specify that copies should strictly be put on
different disks. In this we we can get level of protection close to that
of a mirror and a much greater flexibility - for example, for two disk
systems we may have two copies for boot environment and critical data,
and use only one copy for data that is temporary. This may be a first
step on a way to implementation of redundancy on filesystem, directory
or file basis.
I see no need for additional non-guaranteed reliability on top of the
levels of guaranty provided by use of redundancy at the pool level.
Furthermore, as others have pointed out, this feature would add a high
degree of user-visible complexity.
From what I've seen here so far, I think this is a bad idea and should
not be added.
I think that with a way to specify policy of placing copies I think this
is a good and useful idea, and it's a pity that it is shelved for now.
Hope it will not stay on the shelf forever ;-)
Victor
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