Re: inferior SCSI performance

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От Ang Chin Han
Тема Re: inferior SCSI performance
Дата
Msg-id 3F7BE7B1.5090005@bytecraft.com.my
обсуждение исходный текст
Ответ на Re: inferior SCSI performance  (Andrew Sullivan <andrew@libertyrms.info>)
Список pgsql-performance
Andrew Sullivan wrote:

> Yes.  If and only if you have a battery-backed cache.  I know of no
> IDE drives that have that, but there's nothing about the spec which
> makes it impossible.

http://www.ussg.iu.edu/hypermail/linux/kernel/0103.0/1084.html

Relevant section:
<quote>
Maybe that is why there is a vender disk-cache dump zone on the edge of
the platters...just maybe you need to buy your drives from somebody that
does this and has a predictive sector stretcher as the energy from the
inertia by the DC three-phase motor executes the dump.

Ever wondered why modern drives have open collectors on the databuss?
Maybe to disconnect the power draw so that the motor now generator
provides the needed power to complete the data dump...
</quote>

SEEMS to imply that some IDE drives at least have enough power left
after power's off to store the write-cached data to disk.

The rest of the email's not very reassuring, though, but note that this
email's two years old.

Anyone want to test? :)

--
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