Hi Timothy,
On Sunday 27 July 2008 14:10, timothy norman huber wrote:

quoted text
> Daniel,

>

> Several weeks ago, during a discussion over coffee, you mentioned a

> rather intriguing optimization- by writing the start of the forward

> log chain to NVRAM rather than disk, you avoid a disk seek and write

> transfer for each forward log chain.  i believe there was another

> motivation that had to do with avoiding traversing the entire volume

> in case of a crash.  Was this design feature to overcome lame fsck

> performance?

The same motivation, actually.  Writing the start of a forward log

chain to nvram instead of to some known location on disk means that I

do not have to worry about doing unnatural things to optimize such

loads as O_SYNC writing, where each transaction has to complete

before the next one can begin, which means that the forward log chain

never gets more than one element log, requiring a seek to the known

location for every transaction.  Not worse than journalling to be

sure, and usually better, but not as fast as avoiding a seek and disk

write per transaction entirely.
So if somebody could give me 16 bytes of NVRAM or so per volume I

would be most pleased and could use that to generate some nice O_SYNC

benchmarks :-)
By the way, I wonder why your posts do not show up in the Mailman

(Pipermail) archive, while mine and Matt's do?
Daniel
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