[Firebird-devel] Shadow files

[Kjell R. <kje...@da...>]

Hi,

In a fb-support discussion it has occurred to me and Karol Bieniaszewski 
that the old shadow file feature is actually useful for some purposes.

Karol runs the master on a RAM disk to make sure reads and searches are 
as fast as possible, and has a shadow file on a regular disk to protect 
against data loss on power failures. We will soon have a somewhat 
similar setup.

So, I ask you in the devel team: is the shadow file feature going to go 
away or will you make sure it stays functional?

If it will be removed, what would you say is a viable alternative to 
achieve the same thing with a RAM disk + regular disk combo?

Is replication a viable option? Perhaps even better? Why? Pros & cons?

I can imagine that the shadow file technology will incur regular disk 
latencies on all writes (including header updates for read only 
transaction), while replication would allow updates to "return" after 
updating only the RAM master and read only transactions would only touch 
the RAM disk header - thay wouldn't be replicated at all.

So, what would be the downsides of replication as opposed to shadow 
file? Higher risk of data loss? If so, how/why? What else?

Regards,
Kjell
-- 
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Kjell Rilbe
DataDIA AB
E-post: kj...@da...
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