From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roy Sigurd Karlsbakk Subject: Re: Checksumming RAID? Date: Wed, 28 Nov 2012 20:18:15 +0100 (CET) Message-ID: <31757832.29.1354130295835.JavaMail.root@zimbra> References: <952F7343-6478-417E-BA06-D1B0E36519E0@colorremedies.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <952F7343-6478-417E-BA06-D1B0E36519E0@colorremedies.com> Sender: linux-raid-owner@vger.kernel.org To: Chris Murphy Cc: Linux Raid List-Id: linux-raid.ids > > That doesn't make sense. Nearline and enterprise drives are large > > 7k2 drives that come in consumer and enterprise models, >=20 > Nearline drives are in between consumer and enterprise. Well, they are named enterprise=E2=80=A6 > > Comparing "nearline" and "enterprise" like done here, is merely a > > comparison of small and large drives, where it's well known that th= e > > smaller (less dense) drives have less errors. >=20 > The paper I cited doesn't support this. The nearline SATA with > hardware adapters to convert the interface to fibre channel. The > enterprise drives were already fibre channel. The paper discusses the > contribution of the adapter to checksum mismatches, but this alone > doesn't account for all of the higher rate of error in nearline SATA. 7k2 "nearline" SAS drives exist from several vendors, with SAS interfac= es without the need for adapters. Also, the interface, wheather SAS or = SATA or FC, doesn't really mean much when the drive is the same. SAS (a= nd FC?) has better timing and better controllers, but a SAS drive is a = SAS drive nonetheless if it has a SAS interface. > Further, the paper says "There is no clear indication that disk size > affects the probability of developing checksum mis- matches." >=20 > At least when it comes to URE (which is not SDC), we note that the > manufacturer specs are the same for a model regardless of disk size. Then, if this is true, perhaps they should name their 4TB drives someth= ing else than "enterprise", which they do. Do you have more references = on this part? Vennlige hilsener / Best regards roy -- Roy Sigurd Karlsbakk (+47) 98013356 roy@karlsbakk.net http://blogg.karlsbakk.net/ GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt.= Det er et element=C3=A6rt imperativ for alle pedagoger =C3=A5 unng=C3=A5= eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilf= eller eksisterer adekvate og relevante synonymer p=C3=A5 norsk. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html