From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [Bug 13499] Write cache: disabled, read cache: enabled, supports DPO and FUA? it's bug??? Date: Wed, 10 Jun 2009 14:14:07 +0000 Message-ID: <1244643247.4109.9.camel@mulgrave.site> References: <200906101400.n5AE0rtK002962@demeter.kernel.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:59198 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754251AbZFJOOJ (ORCPT ); Wed, 10 Jun 2009 10:14:09 -0400 In-Reply-To: <200906101400.n5AE0rtK002962@demeter.kernel.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: bugzilla-daemon@bugzilla.kernel.org Cc: linux-scsi@vger.kernel.org On Wed, 2009-06-10 at 14:00 +0000, bugzilla-daemon@bugzilla.kernel.org wrote: > why Write cache: disabled?? The SCSI mid layer is merely reporting what your array is telling it. For arrays without a battery backed cache, write through configuration (i.e. read cache enabled, write cache disabled) is the usual safe default. You can alter your write cache settings using Doug Gilbert's sg3-utils ... but be warned, enabling the write cache without battery backing in an array is a dangerous thing to do since most arrays have huge caches, they either ignore SYNCHRONIZE CACHE (which would leave you vulnerable to data loss on power failure) or take such a long time, it would kill performance. James