So you're saying LMDB looking up a user-specific record and returning it will always be faster than either an lseek() and read() on a cached mmapped file [old model] or an open(), read(), close() on a cached file [new model] ? Is the Linux VFS that slow?
In terms of transaction guarantees, I thought the commenter was talking about the newer model where each profile is an independent (and tiny) file; if that's the case, then deleting and renaming files wouldn't be necessary, and any failures in writing could be rolled back in the journal rather than be a file that's now non-existent or renamed. From what I understand, the most the ext4 issue would affect this newer model would be to revert newly-created profile files, which again I think would be a minor setback for this forum.
In terms of transaction guarantees, I thought the commenter was talking about the newer model where each profile is an independent (and tiny) file; if that's the case, then deleting and renaming files wouldn't be necessary, and any failures in writing could be rolled back in the journal rather than be a file that's now non-existent or renamed. From what I understand, the most the ext4 issue would affect this newer model would be to revert newly-created profile files, which again I think would be a minor setback for this forum.