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Re: 500 tpsQL + WAL log implementation

From: Jan Wieck <JanWieck(at)Yahoo(dot)com>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Curtis Faith <curtis(at)galtcapital(dot)com>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: 500 tpsQL + WAL log implementation
Date: 2003-05-26 18:20:56
Message-ID: 3ED25B08.5000101@Yahoo.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Bruce Momjian wrote:
> Jan Wieck wrote:
> 
>>Bruce Momjian wrote:
>>
>>>[...]
>>>If we could somehow know the platter location, or tell the disk drive to
>>>write it in several locations, whichever is closest, I think we would
>>>have a real win.  However, I don't see any way of doing that.
>>>
>>>Imagine what we could do with 8mb of battery-backed RAM!  This is sort
>>>of what we are using WAL/disk for, and it really isn't very good at it.
>>
>>Isn't that what modern disk drives have ... well, not exactly battery 
>>backed, but actually the energy they have in the rotation is enough to 
>>flush the "write cache" out to the surface and get the heads back into 
>>the parking position in the case of a power loss.
> 
> 
> That's what I am not sure about --- if those drives return a 'complete'
> before getting the actual data on the drive, then we don't have a
> rotational delay problem because it isn't waiting for the platter to
> spin into place, _and_ the data is secure.

The option is called "Immediate SCSI Error Reporting" ;-)


Jan

-- 
#======================================================================#
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