From: Helen B. <he...@tp...> - 2007-09-28 15:00:31
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At 12:37 AM 29/09/2007, Alex wrote: >After fixing http://tracker.firebirdsql.org/browse/CORE-1476 By "fixing" do you mean synch writes now work on Linux as we always thought they did, or that you can achieve FW=ON only by writing to a raw device? The other question I have is this: have you thought of some way to monitor the capacity of the raw device? AFAIR, the engine does not (cannot) request blocks from the OS for a raw device so the engine has no way to know whether there is enough space there to fulfil a request. >Location DIRECT_IO=on DIRECT_IO=off >ext3fs 2m 13s 0m 27s >raw device 0m 34s 0m 20s > >You may see that it looks like now I know an answer to question 'What for do >we need that raw devices?'. We need it to accelerate operation in forced >write mode. Specially of we need DIRECT_IO to save memory for cache. > >I wonder - may be it's time to document that feature in 2.1? I would like to document it, but only if it can be documented without guessing and with some determinate assessment of the pitfalls. Could we have some conclusive discussion about it first? Perhaps, if it is possible to shadow a db to a raw device, someone might be willing to soak it well and feed back... Helen |