From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kent Overstreet Subject: Re: 4K sectors Date: Mon, 13 Aug 2012 14:12:27 -0700 Message-ID: <20120813211227.GA6887@google.com> References: <6035A0D088A63A46850C3988ED045A4B299F682F@BITCOM1.int.sbss.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <6035A0D088A63A46850C3988ED045A4B299F682F-mzsoxcrO4/2UD0RQwgcqbDSf8X3wrgjD@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: James Harper Cc: "linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-bcache@vger.kernel.org On Mon, Aug 13, 2012 at 07:19:50AM +0000, James Harper wrote: > I notice on my system that bcache presents 4K sectors to Linux. This is causing me problems with Windows on Xen using my PV drivers (problem = doesn't work). I haven't figured out if it's my PV drivers that don't tell Windows the right thing, or if Windows just doesn't like 4K sectors. > > Is the 4K sector thing intentional? I assume there is a performance improvement in doing so. It is intentional, but it's configurable. It's mainly for devices that don't support < 4k writes; there might also be a performance impact with some SSDs but I'm sure it's slight. You'll need to reformat - pass --block 512 to make-bcache. The backing devices need to be reformatted too, but just rerunning make-bcache won't touch any of the existing data. > > And what would be the performance impact if I just told Windows that it was dealing with 512 byte sectors (eg fake it)? > > Thanks > > James > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html