Re: Scaling further up
От | Paul Thomas |
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Тема | Re: Scaling further up |
Дата | |
Msg-id | 20040304005208.A25816@bacon обсуждение исходный текст |
Ответ на | Re: Scaling further up ("scott.marlowe" <scott.marlowe@ihs.com>) |
Ответы |
Re: Scaling further up
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Список | pgsql-performance |
On 03/03/2004 18:23 scott.marlowe wrote: > [snip] > There are three factors that affect how fast you can get to the next > sector: > > seek time > settle time > rotational latency > > Most drives only list the first, and don't bother to mention the other > two. Ah yes, one of my (very) few still functioning brain cells was nagging about another bit of time in the equation :) > On many modern drives, the seek times are around 5 to 10 milliseconds. > [snip] Going back to the OPs posting about random_page_cost, imagine I have 2 servers identical in every way except the disk drive. Server A has a 10K rpm drive and server B has a 15K rpm drive. Seek/settle times aren't spectacularly different between the 2 drives. I'm wondering if drive B might actually merit a _higher_ random_page_cost than drive A as, once it gets settled on a disk track, it can suck the data off a lot faster. opinions/experiences anyone? -- Paul Thomas +------------------------------+---------------------------------------------+ | Thomas Micro Systems Limited | Software Solutions for the Smaller Business | | Computer Consultants | http://www.thomas-micro-systems-ltd.co.uk | +------------------------------+---------------------------------------------+
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