From mboxrd@z Thu Jan 1 00:00:00 1970 From: jshankar Subject: RE: queue depth help!! Date: Wed, 31 Dec 2003 09:23:27 -0700 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <3FF4A594@webmail.colostate.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from chico.cs.colostate.edu ([129.82.45.30]:47867 "EHLO chico.cs.colostate.edu") by vger.kernel.org with ESMTP id S265193AbTLaQXa (ORCPT ); Wed, 31 Dec 2003 11:23:30 -0500 List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: linux-scsi Hello James, Case :queue depth=1 On issuing a scsi command write, does the data needs to be written succesfully to disk before issuing a scsi response. Is there a chance that the previous command's data is still cached on scsi controller and the next command issued is executed. Please let me know if there are any good tools for scsi analyzer. Thanks Jay >===== Original Message From James Bottomley ===== >On Sat, 2003-12-27 at 15:38, jshankar wrote: >> if the scsi target queue depth is 1, does it mean that i can handle only one >> outstanding command at a time. > >Yes > >> Does it mean if another command is issued( queue depth=1), it has to wait till >> the previous command is done. > >Yes. > >The mid-layer will start the queued command as soon as the one occupying >the device returns...this is often why untagged devices actually set >their depth to 2 so they can have another command all prepared and ready >to roll as soon as the in-progress one returns. > >James