Date: Fri, 1 Jan 2010 10:56:21 -0600 (CST) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Danny Carroll <danny@dannysplace.net> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS RaidZ2 with 24 drives? Message-ID: <alpine.GSO.2.01.1001011050280.1586@freddy.simplesystems.org> In-Reply-To: <4B3D95AD.8050304@dannysplace.net> References: <568624531.20091215163420@pyro.de> <42952D86-6B4D-49A3-8E4F-7A1A53A954C2@spry.com> <957649379.20091216005253@pyro.de> <26F8D203-A923-47D3-9935-BE4BC6DA09B7@corp.spry.com> <4B3D95AD.8050304@dannysplace.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, 1 Jan 2010, Danny Carroll wrote: > > You do not have this protection when ZFS has access to the raw devices. > Even worse if the devices write cache is turned on. This statement does not appear to be true. ZFS will always request that devices flush their cache. The only time there is no "protection" is if the device ignores that flush request and the cache is volatile. Controller battery-backed RAM is useful since the controller can respond to the cache flush request once the data is in battery-backed RAM, thereby dramatically improving write latencies for small writes Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?alpine.GSO.2.01.1001011050280.1586>