On 04/02/2012 06:20 AM, MORITA Kazutaka wrote:
> If you don't mind disabling O_DSYNC for a object cache, please support
> following flags:
>
> * for users who run VMs in Sheepdog cluster
>
> - (O_DIRECT|O_DSYNC|O_RDWR) for backend stores
> - (O_DIRECT|O_RDWR) for object caches
>
> It is because we want to use a host memory for guest VMs.
>
> * for users who run VMs outside Sheepdog cluster
>
> - (O_DIRECT|O_DSYNC|O_RDWR) for backend stores
> - only O_RDWR for object caches
>
> It is because we can use a memory on the storage node for disk
> caches of Sheepdog virtual disks. If you don't mind, I'd like to
> make this option default since it shows the best storage
> performance.
>
I think we'd better not use O_DIRECT even for backend stores as default.
So I'd suggest:
use '-D' or '-directio' to control both object cache and backend stores
whether use page cache or not.
And for object cache, use write-back disk cache. (NO O_DSYNC)
for backend store, do not use write-back disk cache.(YES O_DSYC)
how do you think of it?
Thanks,
Yuan
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