On my new configuration the bset unwritten key bytes are non-zero whereas on older config that is zero: btree nodes: 1192 written sets: 2377 unwritten sets: 1186 written key bytes: 204048256 unwritten key bytes: 115448 floats: 68721067953 failed: 367 What does that indicate? Also, could you please clarify on how advertising stripe size would affect writearound cache mode? - Pradeep Jindal On Tue, Mar 29, 2016 at 1:56 AM, Pradeep Jindal <praddyjindal@xxxxxxxxx> wrote: > 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
