Steffen Heil wrote:

>Hi
>
>
>
>>If one were to create a database inside a ram disk, and have a shadow
>>
>>
>database on physical disk, would it yield any performance benefits, and have
>protection against loss of power, due to the shadow DB on a real storage
>device?
>
>This makes absolutely no sense.
>
>First, if you want to have all you database an a ram drive, you need as much
>memory, as your database could grow to available as ramdrive. Additionally,
>you need to give firebird a lot of ram to run fast.
>
>Why don't you simply enlarge the page cache size for firebird? If firebird
>has enough memory for itself, it will keep pages in memory after the first
>access to them. This will be much faster than your ram drive, since firebird
>will only access information within it`s page cache. So, if you have a huge
>ram drive and less ram for firebird, firbird will start swaping pages
>between its page cache and the ram drive. If you give the memory, you plan
>to use for you ram drive to firebirds page cache, it won't need to do this,
>and access will be equally fast or even faster.
>
>The write order nightmare, a shadow would require will simply be
>non-existend.
>
>So why would you still even consider using a ram drive ?
>
>Regards,
> Steffen
>
>

Steffen,

If you increase the number of cache pages beyond 10000 FB will slow down....

There is another level of cache there is not mentioned.... the OS cache....

I think if you have a lot of RAM and even with a low number of cache
pages, the OS will cache the data by itself.... Anyone will correct if I
am wrong here.... :-)

See you !

--

Alexandre Benson Smith
Development
THOR Software e Comercial Ltda.
Santo Andre - Sao Paulo - Brazil
www.thorsoftware.com.br