From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Scobie Subject: Re: OT: Tips for good hard drives for a home server Date: Sat, 15 Nov 2008 06:47:16 +1300 Message-ID: <491DB9A4.7080308@sauce.co.nz> References: <3ECBDC05781B3D48ABD520A01ABF2F9B299C974A5A@SE-EX008.groupinfra.com> <7d86ddb90811120619vca13676tb0192676ece0cb93@mail.gmail.com> <491CA255.4070402@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mikael Abrahamsson Cc: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids Mikael Abrahamsson wrote: > On Fri, 14 Nov 2008, Billy Crook wrote: > >> Obviously RAID-class drives benefit in hardware raid (with hardware >> raid controllers). But do RAID-class drives benefit when used on a >> non-raid hardware controller, with linux software raid (mdadm)? What >> about a hardware raid controller in JBOD mode? > > This is not a HW vs SW issue, it has to to with the behaviour of the > drives in conjunction with the OS when a certain thing happens. > > In a non-raid environment, you want to read the data at any cost, so > waiting 2 seconds for it to read is no real problem, you just want the > data. > > In a raid environment you can reproduce the block by way of mirror or > parity, so you want the read to fail after a short time so it won't delay > the reading of the data. Here is a paper about the Western Digital feature "TLER", which is used in all their RE series RAID drives. http://www.wdc.com/en/library/sata/2579-001098.pdf In addition, these drives are better able to cope with the problem of mechanical vibration/resonance that occurs when multiple drives are mounted in close proximity: http://www.wdc.com/en/library/sata/2579-001079.pdf These features will benefit HW and SW RAID implementations. I have no association with Western Digital, other than as a satisfied user. Regards, Richard