From owner-freebsd-questions@FreeBSD.ORG Thu Oct 7 10:50:56 2004 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 24CDE16A4CE for ; Thu, 7 Oct 2004 10:50:56 +0000 (GMT) Received: from sdf.lonestar.org (ol.freeshell.org [192.94.73.20]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3411243D45 for ; Thu, 7 Oct 2004 10:50:55 +0000 (GMT) (envelope-from pieckiel@sdf.lonestar.org) Received: from sdf.lonestar.org (IDENT:pieckiel@sverige.freeshell.org [192.94.73.4]) by sdf.lonestar.org (8.12.10/8.12.10) with ESMTP id i97Aoofl026685; Thu, 7 Oct 2004 10:50:50 GMT Received: (from pieckiel@localhost) by sdf.lonestar.org (8.12.10/8.12.8/Submit) id i97Aoo0S007802; Thu, 7 Oct 2004 06:50:50 -0400 (EDT) Date: Thu, 7 Oct 2004 06:50:50 -0400 From: "Kevin A. Pieckiel" To: Dan Nelson Message-ID: <20041007105050.GA7349@SDF.LONESTAR.ORG> Mail-Followup-To: Dan Nelson , freebsd-questions@freebsd.org References: <20041007025138.GA19296@SDF.LONESTAR.ORG> <20041007032416.GK3848@dan.emsphone.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041007032416.GK3848@dan.emsphone.com> User-Agent: Mutt/1.4.2.1i cc: freebsd-questions@freebsd.org Subject: Re: Tape xfers topping out at 10K per transaction? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Oct 2004 10:50:56 -0000 On Wed, Oct 06, 2004 at 10:24:16PM -0500, Dan Nelson wrote: > In the last episode (Oct 06), Kevin A. Pieckiel said: > > I've got an Exabyte M2 connected to my system. I'm running version > > 5.2.1 and have seen this drive do 64K transfers with "systat -vm" > > before (although that was under version 4.9). I can't for the life > > of me find out why I'm only getting 10K per transaction while I'm > > reading from my tape now. At the rate it's going, it will take over > > 10 hours to read through the entire thing. I know the tape drive is > > capable of reading an entire tape in about three hours. > > Tar defaults to a 10k blocksize. When creating tapes, use the 'b' > flag to specify blocksize in 512-byte units. For a 64k blocksize: > "tar cvbf 128 /dev/sa0 /usr" I hit the same 10K limit when I use something like this: # dd if=/dev/nsa0 of=/dev/null bs=64k Is that because tar wrote to the tape with a 10k bock size that even dd can't read larger blocks? That doesn't seem likely to me, but then again, what do I know?