Re: Detailed info on the B-tree store? Native implementations thereof?

[Jason Davies]

On 12 Aug 2009, at 00:08, Robert Newson wrote:

The worst problem is that the disk controller will reorder sector  
writes to reduce seek time, which in effect means that if power is  
lost, some random subset of the last writes may not happen. So you  
won't just end up with a truncated file

But what about that issue? It think it's tolerated because couchdb
searches backward for the last non-corrupt header, right?

find_header(_Fd, -1) ->
   no_valid_header;
find_header(Fd, Block) ->
   case (catch load_header(Fd, Block)) of
   {ok, Bin} ->
       {ok, Bin};
   _Error ->
       find_header(Fd, Block -1)
   end.


What if the tail-header isn't corrupted but some of the preceding  
writes were, due to the tail-header being written before preceding  
blocks?

--
Jason Davies

www.jasondavies.com