From owner-freebsd-hackers@FreeBSD.ORG Fri Mar 27 00:00:25 2015 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 5AEA287E for ; Fri, 27 Mar 2015 00:00:25 +0000 (UTC) Received: from ipmail06.adl6.internode.on.net (ipmail06.adl6.internode.on.net [150.101.137.145]) by mx1.freebsd.org (Postfix) with ESMTP id E0A4EED9 for ; Fri, 27 Mar 2015 00:00:24 +0000 (UTC) Received: from ppp121-45-104-240.lns20.adl6.internode.on.net (HELO midget.dons.net.au) ([121.45.104.240]) by ipmail06.adl6.internode.on.net with ESMTP; 27 Mar 2015 10:25:13 +1030 Received: from [10.0.2.26] ([10.0.2.26]) (authenticated bits=0) by midget.dons.net.au (8.15.1/8.14.9) with ESMTPSA id t2QNt5ek020669 (version=TLSv1 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 27 Mar 2015 10:25:10 +1030 (CST) (envelope-from darius@dons.net.au) Subject: Re: Seagate Archive HDD Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2070.6\)) Content-Type: text/plain; charset=us-ascii From: "O'Connor, Daniel" In-Reply-To: <55148E42.80708@delphij.net> Date: Fri, 27 Mar 2015 10:25:05 +1030 Content-Transfer-Encoding: quoted-printable Message-Id: <4F65B315-5FFE-4184-91FD-C05A40E0A26E@dons.net.au> References: <55148E42.80708@delphij.net> To: d@delphij.net X-Mailer: Apple Mail (2.2070.6) X-Spam-Score: -2.899 () ALL_TRUSTED,BAYES_00,URIBL_BLOCKED X-Scanned-By: MIMEDefang 2.75 on 10.0.2.1 Cc: freebsd-hackers@freebsd.org, Wojciech Puchar X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 Mar 2015 00:00:25 -0000 > On 27 Mar 2015, at 09:24, Xin Li wrote: > On 03/26/15 03:26, Wojciech Puchar wrote: >> http://www.storagereview.com/seagate_archive_hdd_review_8tb >>=20 >> i want to buy 2 such drives for backup server. >>=20 >> This drives use shingled recording. >>=20 >> Are anyone using them and can confirm they are compatible on >> software level with other disks? I understand average random write >> time would be 5-10 times slower than normal drive because of the >> need of rewrite few full tracks worth of data, but otherwise will >> then be compatible and can i use it as usual? >=20 > My understanding is that the SMR drives are actually different class > of storage device. >=20 > The "drive managed" drives as shipped now tries to emulate normal hard > drive's behavior but they present unique risks: for instance, a > rewrite of a small block may end up in a read-modify-write of a much > larger area, so we must refrain from doing such operations for > critical file system data structure, probably by reorganizing the > on-disk format to satisfy the need. I don't think this is necessarily true - I watched a very informative = presentation about SMR drives - = https://www.usenix.org/conference/fast15/technical-sessions/presentation/a= ghayev The drive has many regions with guard bands so it doesn't have to = rewrite the entire disk for certain writes (it may have to rewrite a = whole band though) It also has a log section which it writes to and then back fills into = the shingled area later. The upshot is that you get very weird latencies, but generally writing = sequentially is OK. Random read is OK, random write is utterly abysmal = (duh). One thing I would like to know is if the drive supports TRIM so it can = avoid rewriting a band or not. -- Daniel O'Connor "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C