From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Some very basic questions Date: Wed, 22 Oct 2008 21:22:08 +0200 Message-ID: <48FF7D60.70600@redhat.com> References: <20081021132322.271ad728.skraw@ithnet.com> <1224597580.27474.93.camel@think.oraclecorp.com> <1224622451.7412.1.camel@telesto> <48FE553D.80501@redhat.com> <1224642544.7189.17.camel@telesto> <48FF038A.4010105@redhat.com> <48FF0625.6040400@kernel.org> <48FF2343.3070107@redhat.com> <48FF276B.6090602@kernel.org> <48FF296F.9060009@redhat.com> <48FF515B.2030209@kernel.org> <48FF71BA.8040206@redhat.com> <48FF7B4D.80004@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: Tejun Heo , linux-btrfs@vger.kernel.org To: jim owens Return-path: In-Reply-To: <48FF7B4D.80004@hp.com> List-ID: jim owens wrote: >>> For most SATA drives, disabling write back cache seems to take high >>> toll on write throughput. :-( >> >> I measured this yesterday. This is true for pure write workloads; >> for mixed read/write workloads the throughput decrease is negligible. > > Different tests on different hardware > give different results at different times! > True. But data loss is forever! >> >> I got flamed for this on another list, but let's disable the write >> cache and live with the performance drop. > > We don't get to decide this, customers do. We get to pick the defaults. > As they say in the raid forum... fast, cheap, good - pick any 2 We can upgrade slow to fast, but !good gets upgraded to another fs. > P.S. no flames because we chose no-battery == disable-write-cache ACK! -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.