Re: [Qemu-devel] (iSCSI-)Readcache in Qemu?

[Kevin Wolf]

Am 22.02.2013 um 08:51 hat Peter Lieven geschrieben:
> is there any project or plans to integrate a readcache in qemu either for 
> iscsi or for the whole block layer?
> 
> I was thinking of 2 options:
> a) assign (up to) a fixed amount of ram for readcaching of a VMs disk I/O. 
> Without SG_IO this seems
> to be quite easy as there are only a handful of operations to intercept.
> b) add SSDs to a Node and allow a VM to use up to X MB of that SSD as 
> read-cache. This should still be
> a benefit if the storage for the VMs is on a NAS.
> 
> I would like to do that independent of the OS for 2 reasons. First with iSCSI 
> the OS
> is not involved. And second I would like to be able to add a memory limit for 
> the cache.

I'm not aware of any such plans, but if anyone wanted to write this, I
think the right way to approach it would be as a new block driver that
acts as a filter - for which we still don't have proper support, but if
blkdebug/blkverify work, this could work as well.

Kevin