Re: ZFS License and Future

On 8 November 2010 22:35, Roland Smith <rsmith@xxxxxxxxx> wrote:

On Mon, Nov 08, 2010 at 09:44:29PM +0100, C. P. Ghost wrote:
On Mon, Nov 8, 2010 at 7:38 PM, Roland Smith <rsmith@xxxxxxxxx> wrote:
On Mon, Nov 08, 2010 at 05:08:33PM +0100, Svein Skogen (Listmail
account) wrote:
But it's still not capable of true forward-error-correction. If we are
to embark upon creating a new solution, using something that is cheap
for "normal cases" but can still be used (albeit more expensively) for
error recovery would (imho) be better. Even if that means we get less
net storage out of the gross pool (it could perhaps be configurable?)

I'm not sure what you mean by "true forward-error-correction". But if
you want
to make _really sure_ that a spinning disk hasn't mangled the data you
should:

Maybe something like Reed-Solomon ECC in different blocks.
Should a data block go bad, it could be rebuilt on-the-fly from
those ECC blocks:

And how do you detect that a block has gone bad, other than reading back
what
you wrote and finding a difference? Because that would still be slow.

Roland
-y
R.F.Smith http://www.xs4all.nl/~rsmith/<http://www.xs4all.nl/%7Ersmith/>
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The read doesnt need to be done at write time, it only needs to be done when
the block is read by the system. If an issue is found than the corrective
measures are executed. For you important data in my opinion you should
always set the copies attribute to 3. This is obviously very costly in terms
of storage but its just a trade off for the data.
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Relevant Pages

  • Re: ZFS License and Future
    ... for "normal cases" but can still be used (albeit more expensively) for ... error recovery would be better. ... Maybe something like Reed-Solomon ECC in different blocks. ... Should a data block go bad, it could be rebuilt on-the-fly from ...
    (freebsd-questions)
  • Re: ZFS License and Future
    ... for "normal cases" but can still be used (albeit more expensively) for ... error recovery would be better. ... Maybe something like Reed-Solomon ECC in different blocks. ... Should a data block go bad, it could be rebuilt on-the-fly from ...
    (freebsd-questions)