At Mon, 2 Apr 2012 16:21:11 +0800, Liu Yuan wrote: > > From: Liu Yuan <tailai.ly at taobao.com> > > We async flush dirty object as default to achieve the best performance. > If users prefer strong consistency over performance, users can launch > sheep with -S or --sync option. > > We need async flush because: > 1) some APP are responsive time sensitive, the writeback of dirty bits in > the guest will mostly hurt RT because guest need to await its completion. > This is a considerably long operation in the sheep cluster. > 2) some APP are just memory and CPU intensive, has little of concern of disk > data. (For e.g, just use disk to store logs of APP) > 3) People simply prefer performance over consistency. Sheepdog is a block device storage. This kind of feature must NOT be default. In addition, we had better show a warning about a risk of reading old data, which could cause a filesystem corruption, when users enable this feature. Kazutaka |