From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Some very basic questions Date: Wed, 22 Oct 2008 09:15:05 +0200 Message-ID: <48FED2F9.1060103@redhat.com> References: <20081021173714.29505.qmail@splitreflection.com> <48FE36BD.6020701@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: Stephan von Krawczynski , linux-btrfs@vger.kernel.org To: jim owens Return-path: In-Reply-To: <48FE36BD.6020701@hp.com> List-ID: jim owens wrote: > > Remember that the device bandwidth is the limiter so even > when each host has a dedicated path to the device (as in > dual port SAS or FC), that 2nd host cuts the throughput by > more than 1/2 with uncoordinated seeks and transfers. That's only a problem if there is a single shared device. Since btrfs supports multiple devices, each host could own a device set and access from other hosts would be through the owner. You would need RDMA to get reasonable performance and some kind of dual-porting to get high availability. Each host could control the allocation tree for its devices. Of course, this doesn't solve the other problems with parallel mounts. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.