From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Pearson Subject: Re: LTO-3 read performance issues Date: Thu, 08 Nov 2007 15:10:07 +0000 Message-ID: <473326CF.8060102@moving-picture.com> References: <4731D72D.5000404@moving-picture.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mpc-26.sohonet.co.uk ([193.203.82.251]:37115 "EHLO moving-picture.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752087AbXKHPKJ (ORCPT ); Thu, 8 Nov 2007 10:10:09 -0500 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Kai Makisara Cc: linux-scsi@vger.kernel.org Kai Makisara wrote: >> >>I am using the default st module options and not doing anything other than >>using 'mt setblk 0'. >> >>Is there anything I can do to get a decent, sustained read rate from these >>tapes? >> > > If your system can process the data fast enough and the tape blocks are of > the same size, you can try using fixed block mode and buffered transfers. > This allows the driver to use larger SCSI reads. You have to load the st > module with parameter buffer_kbs=xxx, where xxx is, for instance, 1024 (1 > MB buffer). You also have to disable direct i/o with the module parameter > try_direct_io=0 (otherwise buffered transfers are disabled). Thanks, I tried that, but it makes no difference. I also tried increasing the buffer_kbs size by doubling it a few times, but that made no difference either I have now found out that the tapes were written on an SGI system - using a fixed block device and the default options to tar. However, I have to either use 'mt setblk 0' or 'mt setblk 16384' to read anything from these tapes. Just to check that nothing is wrong with my system, I can read an LTO-3 tape previously written on my system, using the default options to tar and the st module - and I get over 40Mb/s on reads, compared with about 400Kb/s I'm getting with these problematic tapes ... Is there anything else I can do to read these tapes at a decent speed? Thanks James Pearson