I am using writearound cache mode and have xfs on bcache device - Pradeep Jindal On Tue, Mar 29, 2016 at 1:52 AM, Pradeep Jindal <praddyjindal@xxxxxxxxx> wrote: > But in my new configuration backing device is a bare disk, no LVM, caching > device is on LVM though. > > On Mar 29, 2016 1:49 AM, "Vojtech Pavlik" <vojtech@xxxxxxxx> wrote: >> >> On Tue, Mar 29, 2016 at 01:35:32AM +0530, Pradeep Jindal wrote: >> >> > > > I am facing a weird problem, I earlier had a configuration wherein >> > > > my >> > > > backing device was a logical volume (LVM) backed by 3 software RAID0 >> > > > arrays having 2x1TB disks each, so totally 6TB of storage for >> > > > backing >> > > > device and 300GB logical volume (LVM) backed by SSD as a caching >> > > > device. Both were configured as a cache set and I was getting around >> > > > 84% cache hit ratio. >> > > > >> > > > Now, I have changed the backing device to a bare (no LVM, no raid) >> > > > 6TB >> > > > disk while everything else stays same (caching device on LVM, 300GB) >> > > > and for exactly same workload I am only getting 58-60% cache hit >> > > > ratio. >> > > > >> > > > I am confused, what could be the reason? >> > > >> > > Full stripe size writes are configured according to the backing >> > > device, >> > > for example. >> >> > Didn't quite get it, could you please elaborate? >> >> Backing devices that advertise a stripe size cause bcache to enable a >> mode where it tries to always write a full stripe to the backing >> devices, hence changing behavior of the cache. >> >> -- >> Vojtech Pavlik >> Director SuSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
