Richard Hipp wrote:
On Thu, Sep 11, 2014 at 5:49 PM, Kees Nuyt <k.n...@zonnet.nl> wrote:
Hi all,
Today I bumped into a presentation about ordering and atomicity
of filesystems that might interest you.
https://www.youtube.com/watch?v=YvchhB1-Aws
The Application/Storage Interface: After All These Years, We're
Still Doing It Wrong
Remzi Arpaci-Dusseau, University of Wisconsin—Madison
Talk at usenix 2014 Published on Sep 4, 2014 by USENIX
Association Videos
Somewhat related to the article drh recently wrote about using
sqlite as an application data store.
Thanks for the link, Kees!
I just finished watching the video. Remzi Arpaci-Dusseau talks about
research (done by he and his graduate students) into how well application
data survives system crashes. Remzi observes that filesystem developers
have worked very hard for many years ensuring that filesystem metadata is
preserved in a crash, but they seem less concerned about protecting
application data.
Remzi developed tools (BOB and ALICE) to study various workloads to see how
vulnerable they were to system crashes. He looked at various
"applications". His definition of "application" includes standalone
programs like Git and Hg, and database servers like PostgreSQL, and
libraries like SQLite and LevelDB. At one point he shows a chart that
counts the number of unwarranted assumptions that the applications make
about filesystem behavior. Such unwarranted assumptions can lead to
corruption following a system crash (or power loss).
SQLite and PostgreSQL came out on top, with just one vulnerability each.
Hg and Git each had many vulnerabilities. In fairness, Remzi points out
that these vulnerabilities assume a "worst case" filesystem and that many
of them might not exist on a modern filesystem like EXT4.
Actually LMDB comes out on top with zero vulnerabilities. I spoke to the UWisc
folks to find out what was the one Atomicity vulnerability they reported in
LMDB and we confirmed that it was not in fact a valid vulnerability.
--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
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