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Re: The old raw devices chestnut.

From: Andrew Hamm <>
Date: Thu, 15 Apr 2004 12:35:03 +1000
Message-ID: <c5ksg3$2p91m$>

Joel Garry wrote:
> Funnily enough, that very reason is the one I've considered most
> important for years:
> ( the "other hand" line has been superceded in more recent versions ).

He-heh - 1996? that would be around the time my engine was under threat. However, dangerous people can do damage to nearly everything. I've also seen LOST engines from people either deleting or moving cooked files. You can run, but you cannot hide.

> I'd add that if you are that close to saturation where a small
> percentage will make such a difference, you probably need some good
> tuning and/or more hardware.

Wellllllll, no. NIMM (not in my mileage)

a 20% improvement is good - why not? It also improves throughput - 20% would be Just About noticable too. But more importantly, it's during periods of heavy sequentials that it kicks in. An overall benefit of 20% will probably give you bursts of much bigger improvements. Like the (Informix) situations I've mentioned such as creating spaces, but also things like light scans, checkpoints (a major bugbear for some people) and of course big sequential reads and builds.

Further (with Informix, once again) the engine can use KAIO, and with the architecture of Informix, this can lead to further significant improvements. It all adds up. Why do you think F1 now make their pedals out of carbon fibre? And they *still* drill 'em out for extra lightness. An Informix engine using raw with KAIO and a decent layout of spaces on the disk can feel very spiffy indeed even compared to one that merely drops KAIO and raw.

Some UNIX platforms with Big Hairy storage boxes do provide device drivers etc that support KAIO by either faking the raw device or just providing the feature. What you do with that hardware depends on the machinery of course. Received on Wed Apr 14 2004 - 21:35:03 CDT

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