Re: ramfs or ram disk
- From: David Roberts <big.dave.roberts@xxxxxxxxxxxxxx>
- To: Josh.Collier@xxxxxxxxxxxx
- Date: Tue, 20 Aug 2013 23:41:07 +0100
A ram disk is generally a virtual disk emulated in RAM. This will provide
you with an apparently very high performance disk drive.
I believe some operating systems do this by default where the /tmp
partition is backed by RAM, this can substantially increase performance
when poor application developers cache small amounts of data to disk that
should have been cached in memory.
It can also cause issues when junk is left in the tmp directory,
artificially restricting the amount of ram the operating system will
allocate to other applications.
OTOH, I have seen using a ram disk as a recommendation for speeding disk
based sorts. This tends to be self defeating, as to generate the RAM disk
requires sacrificing RAM which can force more sorts to spill to disk. In
essence you are turning a general purpose resource that can be used to
speed up multiple functions into a specific resource that will only speed
up functions of one type.
There will be marginal edge cases where this approach will work, but it
wouldn't be my first or second choice for investigation.
Possibly, he may be recommending using an SSD as cache, but these again
wouldn't be my first choice given a performance problem.
If you were restricted to a 32bit architecture for the database or if there
was something else unusual in your architecture, then there might be value
in investigating a ramdisk, but northing you have told me currently
indicates that is the case.
A little further information might be useful: Is there an application on
the database server, bespoke or otherwise? Or any specific other
justification for the ramdisk?
Dave
On 20 Aug 2013 23:06, "Josh Collier" <Josh.Collier@xxxxxxxxxxxx> wrote:
> My dw architect recently suggested that I create a tempFS "ramdisk" to
> increase performance. Honestly I have no idea what he is talking about. I
> am not sure he does either. When googling I am getting information that
> just confuses me. Does anyone here know what he is talking about?
> Oracle 11.2.02
> Redhat 5.4 64bit
> 500gb ram
>
>
> Creating a disk allocation to use as RAM? That sounds like swap to me.
>
> Creating a ram allocation to use as disk, that sounds volatile to me.
>
> If am not making any sense, please ignore :)
>
>
>
> Have a good day.
>
> --
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>
>
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