From owner-freebsd-questions Fri Nov 23 10:59:22 2001 Delivered-To: freebsd-questions@freebsd.org Received: from kraeusen.nbrewer.com (kraeusen.nbrewer.com [208.42.68.65]) by hub.freebsd.org (Postfix) with ESMTP id E36DD37B41B for ; Fri, 23 Nov 2001 10:59:10 -0800 (PST) Received: by kraeusen.nbrewer.com (Postfix, from userid 1001) id 25F971DCA2B; Mon, 19 Nov 2001 19:18:19 -0600 (CST) Date: Mon, 19 Nov 2001 15:07:13 -0600 From: Christopher Farley To: questions@freebsd.org Subject: Slow restores on a DLT4000 Message-ID: <20011119150711.A7781@northernbrewer.com> Mail-Followup-To: Christopher Farley , questions@freebsd.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.22.1i Organization: Northern Brewer, St. Paul, MN Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG I am a new owner of a pair of DLT4000 drives. I've been testing them using dump and restore. I get fairly good throughput on dumps; about 1.6 megs/second, which seems similar to 'average' expectations that have been published. During a dump, the drive does not stream, but runs, stops, rewinds, runs, stops, rewinds... My thinking is that the tape drive is able to write to a tape faster than my platters can provide the bits. Restoring data off a level 0 dump takes about twice as long as the dump itself, and it also fails to stream. Also, it takes just as long to retrieve a few files off of a dump as it does to restore an entire dump. It seems like the drive simply reads the tape sequentially, and if it sees a file I've marked, it writes it to the disk. Consequently, if the file is at the end of the tape, it will take 4 hours to find the file on a 20 Gig dump. Is this (slow) behavior due to the way dump/restore works, or due to the DLT4000? Is there any kind of drive/backup program that allows for some kind of random access on the tape drive? (I used to have a 4mm DAT, and I seem to recall that restoring a single file or two was very fast and efficient. It has been a while since I've done it, though.) -- Christopher Farley www.northernbrewer.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message