Hello Joe,

Monday, February 23, 2009, 7:23:39 PM, you wrote:

MJ> Mario Goebbels wrote:
>> One thing I'd like to see is an _easy_ option to fall back onto older
>> uberblocks when the zpool went belly up for a silly reason. Something
>> that doesn't involve esoteric parameters supplied to zdb.

MJ> Between uberblock updates, there may be many write operations to
MJ> a data file, each requiring a copy on write operation.  Some of
MJ> those operations may reuse blocks that were metadata blocks
MJ> pointed to by the previous uberblock.

MJ> In which case the old uberblock points to a metadata tree full of garbage.

MJ> Jeff, you must have some idea on how to overcome this in your bugfix, would 
you care to share?

As was suggested on the list before ZFS could keep a list of freed
blocks for last N txgs and if there are still other blocks to be used
it would not allocated those from the last N transactions.


-- 
Best regards,
 Robert Milkowski
                                       http://milek.blogspot.com

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