From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f49.google.com ([209.85.213.49]:34014 "EHLO mail-vk0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802AbdDAGGM (ORCPT ); Sat, 1 Apr 2017 02:06:12 -0400 Received: by mail-vk0-f49.google.com with SMTP id z204so106779449vkd.1 for ; Fri, 31 Mar 2017 23:06:12 -0700 (PDT) MIME-Version: 1.0 Reply-To: matianfu@gmail.com From: UGlee Date: Sat, 1 Apr 2017 14:06:11 +0800 Message-ID: Subject: mix ssd and hdd in single volume To: linux-btrfs@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: We are working on a small NAS server for home user. The product is equipped with a small fast SSD (around 60-120GB) and a large HDD (2T to 4T). We have two choices: 1. using bcache to accelerate io operation 2. combining SSD and HDD into a single btrfs volume. Bcache is certainly designed for our purpose. But bcache requires complex configuration and can only start from clean disk. Also in our test in Ubuntu 16.04, data inconsistence was observed at least once, resulting total HDD data lost. So we wonder if simply putting SSD and HDD into a single btrfs volume, in whatever mode, the general read operation (mostly readdir and getxattr) will also be significantly faster than a single HDD without SSD.