On 22 jan 2011, at 11:10, Mariano Martinez Peck wrote:
On Fri, Jan 21, 2011 at 5:12 PM, Tudor Girba tudor.girba@gmail.com wrote: Just a question: Would the new slate disks not alleviate the problem of the disk speed?
For Gemstone, Hernan Wilkinson did some test 1 o 2 years ago, and the difference was....mmmm I dont remember, but I think 40x faster. All the Gemstone migrations and I don't remember what more, was done with that HDD. So, yes, at least in Gemstone it changes a lot.
Latency for reading is 65-75 microseconds. That is a lot better than hard disks. For writing the situation is different. There SSDs can be comparable to a HD (up to a few times faster) when having to clear a page. You'll only notice this after all pages of the SSD have been written. Before that, performance will be spectacular. Documentation on real (long term) write performance of SSDs is hard to get/interpret.
http://www.slideshare.net/matsunobu/ssd-deployment-strategies-for-mysql
And of course SSDs are still more than 100 times slower than ram.
Stephan