Comments on: I Didn’t Know That 6 – What is Wrong with this Quote?

By: Martin Berger

Martin Berger — Tue, 14 Dec 2010 21:17:38 +0000

I assume ” … network RAM and CPU speeds.” is missing a comma: ” … network, RAM and CPU speeds.” This might make any sense.
Unfortunately the statement is not quite specific at all.
In case of db_flash_cache_file, SSDs might be a good bridge between ram (speed&price) and hdd (speed&price). But even this must be well planned.
I read this quote like ‘if SSD is used for data files, only a little db cache is needed anymore.’ Based on that interpretation I would not compare db-cache speed to IO speed – even with a ram-disk for the data files. Once again not tested/measured I am sure the same data block will be much faster accessed in the chain “search_in_buffer -> hit” against “(search_in_buffer -> fail); tell_OS_to_do_IO; IO_is_done_by_OS; (probably_copy_block_into_buffer); -> hit”. In fact it’s even more complex, but you got the point?

By: Charles Hooper

Charles Hooper — Tue, 14 Dec 2010 14:15:24 +0000

Flado,

Excellent points.
———

Anyone have access to some platter based hard drives from the 1960s that can do a head to head comparison with SSD drives? I know that the hard drives from the early 1990s were able to achieve transfer speeds of 1MB per second, while a Crucial C300 256GB drive that retails for roughly $550 USD is able to hit speeds ranging from 270MB per second to 355MB per second depending on the controller used in the server. (Is this perhaps a hint?)

By: Flado

Flado — Tue, 14 Dec 2010 10:17:33 +0000

Erm…
* People are replacing the DDR RAM traditionally used for “the Oracle data buffer cache” with (Flash, I assume) SSDs? How?! And how replacing the Oracle data buffer cache with a slower storage speeds up I/O at the physical layer?
* What’s “network RAM”?
* SSD has no channel contention? How is that, when even volatile RAM has it?