Re: [boost] NuDB: A fast key/value insert-only database for SSD drives in C++11

On Wed, 29 Mar 2017 12:07:11 -0400 Vinnie Falco via Boost wrote:

On Wed, Mar 29, 2017 at 12:03 PM, Niall Douglas via Boost wrote:

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If he rewrote those two paragraphs above with the below I would have no objection apart from that his design is flawed and should not enter Boost without being substantially redesigned.

I could take this seriously if you provide code in the form of a regression test which shows the scenario in which a power loss harms NuDB database integrity. Because, as they say, "talk is cheap."

Read this [paper on crash-consistent applications][0]. Table 1 on page 5 should be of particular interest. I _think_ the bucket portion of NuDB's log has no size constraint, so its algorithm is either going to be "single sector append", "single block append", or "multi-block append/writes" depending on the total size of the buckets. The algorithm is always problematic when metadata journaling is disabled. Your assumptions of fsync have not been violated to achieve those inconsistencies. A test case could be writing completely random data to the bucket portion of the log to see what happens. The behavior should be indeterminate, because its the equivalent of reading uninitialized memory. Lee [0]https://www.usenix.org/system/files/conference/osdi14/osdi14-paper-pillai.pd...