From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: sd incorrectly reports write cache disabled on cache-capable drives/controllers Date: Fri, 25 Jan 2008 15:33:21 -0600 Message-ID: <1201296801.3119.63.camel@localhost.localdomain> References: <200801252159.20858.yallaone@gmail.com> <1201295720.3119.51.camel@localhost.localdomain> <200801252228.22659.yallaone@gmail.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from accolon.hansenpartnership.com ([76.243.235.52]:46255 "EHLO accolon.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754469AbYAYVd1 (ORCPT ); Fri, 25 Jan 2008 16:33:27 -0500 In-Reply-To: <200801252228.22659.yallaone@gmail.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Halim Issa Cc: linux-scsi@vger.kernel.org On Fri, 2008-01-25 at 22:28 +0100, Halim Issa wrote: > Thank you so much for the quick reply - I risk asking one follow-up question. > > On Friday 25 January 2008 22:15:20 James Bottomley wrote: > > The "cache" hear would be referring to the RAID controller cache, not > > the disk cache. Likewise DPO and FUA refer to what the RAID controller > > can support, not the disk. > > Would it be safe to assume that the problem thus lies within the mptfusion > driver, since a) the LSI Logic controller in question does indeed have > hardware cache capabilities; and b) an older kernel version as well as > Windows Server, correctly loads with the correct cache parameters at boot? I don't think it would be correct to assume that there actually is a problem. Most RAID controllers habitually lie about having a cache in their INQUIRY strings because they don't want to deal with the kernel sending SYNCHRONIZE_CACHE commands down. Just because the inquiry strings say it doesn't have a cache doesn't really mean it's not using one but not telling anyone. James