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Re: LMDB concurrent operation and MDB_NOSYNC
On 04/05/14 19:00, Howard Chu wrote:
> Kristian Amlie wrote:
>> It turns out that LMDB does not work correctly on the AUFS filesystem.
>> Is this known?
>
> No, thanks for that info. The filesystem types we tested are listed here
> http://symas.com/mdb/microbench/july/#sec11
After more investigation, I have found that it takes a very special set
of circumstances to trigger the bug. Basically you have to mount the
same writable directory branch onto two mount points using AUFS, and
then access the database separately from each mount point. This is most
likely a very uncommon setup (*), and I don't think perfect thread
synchronization can be expected from it.
So in short, this is a non-issue, but at least now we know why! :-)
(*) Uncommon, but not unheard of: The "schroot" tool uses this when you
use the "union-type=aufs" option.
--
Kristian