From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f182.google.com ([209.85.216.182]:33986 "EHLO mail-qc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754117AbbFOQHU (ORCPT ); Mon, 15 Jun 2015 12:07:20 -0400 Received: by qcwx2 with SMTP id x2so4190442qcw.1 for ; Mon, 15 Jun 2015 09:07:19 -0700 (PDT) Message-ID: <1434384437.6916.11.camel@kepstin.ca> Subject: Re: multiple "devices" with multiple partitions on one SSD From: Calvin Walton To: Tom Yan , Duncan <1i5t5.duncan@cox.net> Cc: linux-btrfs@vger.kernel.org Date: Mon, 15 Jun 2015 12:07:17 -0400 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, 2015-06-12 at 18:11 +0800, Tom Yan wrote: > Thank you for you reply. I thought of the same thing as you've told, > but because I don't really know how SSD/SATA works internally, so I > was also thinking if "raid0" on the same drive might works as > something like "Hyper-Threading" in CPU. Modern SSD controllers are already effectively doing "RAID0" striping over multiple individual flash chips inside the drive in order to achieve maximum sequential write speeds. With high end drives, a single sequential write can already saturate the available bandwidth on the SATA wire. If anything, splitting up writes to bounce back and forth between two different regions of the same drive would add overhead, and might disrupt the write optimizations in the drive controller. It would probably end up slower - although the difference might not be noticable If you're just looking for speed, stick to single mode and let the drive go fast. Calvin. -- Calvin Walton