From owner-freebsd-hackers@FreeBSD.ORG Thu Nov 17 22:16:55 2011 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D64AC1065673 for ; Thu, 17 Nov 2011 22:16:55 +0000 (UTC) (envelope-from perryh@pluto.rain.com) Received: from agora.rdrop.com (unknown [IPv6:2607:f678:1010::34]) by mx1.freebsd.org (Postfix) with ESMTP id B71888FC13 for ; Thu, 17 Nov 2011 22:16:55 +0000 (UTC) Received: from agora.rdrop.com (66@localhost [127.0.0.1]) by agora.rdrop.com (8.13.1/8.12.7) with ESMTP id pAHMGqWS084236 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Thu, 17 Nov 2011 14:16:53 -0800 (PST) (envelope-from perryh@pluto.rain.com) Received: (from uucp@localhost) by agora.rdrop.com (8.13.1/8.12.9/Submit) with UUCP id pAHMGqP0084235; Thu, 17 Nov 2011 14:16:52 -0800 (PST) Received: from fbsd81 ([192.168.200.81]) by pluto.rain.com (4.1/SMI-4.1-pluto-M2060407) id AA01982; Thu, 17 Nov 11 14:00:56 PST Date: Thu, 17 Nov 2011 21:00:38 -0800 From: perryh@pluto.rain.com To: dieterbsd@engineer.com Message-Id: <4ec5e676.P+DwfO0SrmiegcuB%perryh@pluto.rain.com> References: <20111117175514.274040@gmx.com> In-Reply-To: <20111117175514.274040@gmx.com> User-Agent: nail 11.25 7/29/05 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@freebsd.org Subject: Re: easy way to determine if a stream or fd is seekable X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 17 Nov 2011 22:16:55 -0000 "Dieter BSD" wrote: > IIRC some tape drives can seek, while others cannot. > Vague memories that it is supposed to be possible to put a > filesystem on a DECtape and mount the filesystem. Back in the Bell Labs 6th Edition days, it was possible to put a filesystem on a _9-track magtape_ and mount it, although such a mount had to be read-only since writing to a 9-track would effectively delete any blocks following the one written. I've done it. Access was painfully slow (no surprise), but it did work. DECtape _could_ be updated in place. It was effectively the linear equivalent of a floppy disk (before floppy disks existed). Sequential access was slow. Random access was very slow.