[Gluster-devel] Cache Translator Questions

[Basavanagowda Kanur]

Replies inline.

On Tue, Dec 30, 2008 at 11:11 PM, Martin Fick <mogulguy at yahoo.com> wrote:

> Hi,
>
> I would like to understand the cache translator better.
>
> 1A) Is the cache a memory cache only (non-file based)?

Yes, io-cache is a memory cache.

>
> 1B) If memory only, are there any plans for a file based cache?
>
Yes, we have plans for file based cache in our future release.

>
> 2) Are there any downsides to making the cache very large, simply using up
> memory?
>
You can make have large cache size.

>
> 3) What is the page-size used for? Is it the minimum amount used per file
> cached?
>
page-size is the size of cache page stored in memory by io-cache. io-cache
reads from file in page-size size everytime.

>
> 4A) What is the timeout used for?

timeout is attribute timeout. after timeout time, revalidate is sent and the
io-cache is updated if the attributes have changed.

>
> 4B) Does the client check with the server to see if a file has changed
> before the timeout, or only after?

every read call returns also returns attribute, so revalidation is done even
with read calls. if no read/write activity has happened on file, then
attribute validation is done after timeout.

>
> 4C) Is a file flushed no matter what after the timeout?
>
no file will be flushed only if it has changed or is not used for long time
and cache needs to make space for other files.

>
> Thanks,
>
> -Martin
>
>
>
>
>
>
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>



-- 
gowda
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