Re: [CentOS] Calling All FS Fanatics

[Kirk Bocek <t004@xxxxxxxxxx>]

Feizhou wrote:
> There are two levels of caching. Hardware and software. Hardware level
> caching involves in your case the 3ware card cache and the individual
> disk caches.
> 
> Software level involves the kernel's disk cache.
> 
> There are FS level settings available. You can mount the filesystem with
> the sync option which means writes are to be done synchronously and so
> these are not stored in the kernel's cache. There is also dirsync which
> can to used to ensure metadata on files/directories are also written
> synchronously.
> 
> You can also do it on a per file level by setting the file's sync (S)
> attribute.
> 
> So a completely paranoid setup would include making sure that the
> file/filesystem is sync'ed and also turning off the write cache on the
> hardware. You should be able to set sync at the software level and leave
> the hardware write caching on and see a difference.

So what do *you* do when you disable write caching on one of your systems?

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