From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout.teamix.de ([194.150.191.118]:32868 "EHLO mailout.teamix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755276AbaGIOyn convert rfc822-to-8bit (ORCPT ); Wed, 9 Jul 2014 10:54:43 -0400 From: Martin Steigerwald To: Daniel Pocock CC: Subject: Re: btrfs RAID with enterprise SATA or SAS drives Date: Wed, 9 Jul 2014 16:48:05 +0200 Message-ID: <41327882.AW8TtKTnAV@merkaba> In-Reply-To: <4FAAE94D.4010103@pocock.com.au> References: <4FAAE94D.4010103@pocock.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-btrfs-owner@vger.kernel.org List-ID: Am Mittwoch, 9. Mai 2012, 22:01:49 schrieb Daniel Pocock: > There is various information about > - enterprise-class drives (either SAS or just enterprise SATA) > - the SCSI/SAS protocols themselves vs SATA > having more advanced features (e.g. for dealing with error conditions) > than the average block device > > For example, Adaptec recommends that such drives will work better with > their hardware RAID cards: […] > - for someone using SAS or enterprise SATA drives with Linux, I > understand btrfs gives the extra benefit of checksums, are there any > other specific benefits over using mdadm or dmraid? I think I can answer this one. Most important advantage I think is BTRFS is aware of which blocks of the RAID are in use and need to be synced: - Instant initialization of RAID regardless of size (unless at some capacity mkfs.btrfs needs more time) - Rebuild after disk failure or disk replace will only copy *used* blocks Scrubbing can repair from good disk if RAID with redundancy, but SoftRAID should be able to do this as well. But also for scrubbing: BTRFS only check and repairs used blocks. Another advantage in the future – not yet possible AFAIK: - Different RAID levels on same filesystem yet different subvolumes, more flexibility as subvolumes are dynamically allocated, instead of statically sized Ciao, Martin -- Martin Steigerwald Consultant / Trainer teamix GmbH Südwestpark 43 90449 Nürnberg fon: +49 911 30999 55 fax: +49 911 30999 99 mail: martin.steigerwald@teamix.de web: http://www.teamix.de blog: http://blog.teamix.de Amtsgericht Nürnberg, HRB 18320 Geschäftsführer: Oliver Kügow, Richard Müller ** JETZT ANMELDEN – teamix TechDemo - 23.07.2014 - http://www.teamix.de/techdemo **