proxy_cache ramdisk

[Igor Sysoev]

On Tue, Feb 02, 2010 at 01:19:16AM +0800, quan nexthop wrote:

> HI Igor Sysoev:
> 
> Could you please give us an explaination for these ?
> 
> > Caching in ramdisk is usually not good idea, since there is OS VM cache.
> You just waste memory and CPU time.
> [nexthop]  If we want to get a high performace, can we cache using RAMdisk ?
> According to your comments, it seems that cache in ramdisk have a lower
> performace.
> 
> I do a google search with ramdisk cache, it seems that Cache in RamDisk will
> get a high performance.
> http://lowendmac.com/tech/diskcache.shtml
> 
> I am confusing it.
> Could you please give us more information about it ?

RAMdisk has no lower performace. It just wastes memory: OS stores two copies
of an object: one in OS cache and second in RAMdisk. Some tmpfs
implementations may eliminate this double copy.

> On Tue, Feb 2, 2010 at 12:33 AM, Igor Sysoev <igor at sysoev.ru> wrote:
> 
> >  On Fri, Jan 29, 2010 at 10:44:46AM -0600, AMP Admin wrote:
> >
> > > So I was thinking of creating a ramdisk and then pointing proxy_cache at
> > the
> > > ramdisk. do you think that will be a good combo?
> > >
> > > If so, to the people that use proxy_cache, how much space is it using on
> > > average so I can make it the right size?
> >
> > Caching in ramdisk is usually not good idea, since there is OS VM cache.
> > You just waste memory and CPU time.
> >
> >
> > --
> > Igor Sysoev
> > http://sysoev.ru/en/
> >
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> > nginx at nginx.org
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> >

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-- 
Igor Sysoev
http://sysoev.ru/en/