Date: Mon, 6 Dec 1999 17:12:13 -0800 (PST) From: David Wolfskill <dhw@whistle.com> To: freebsd-newbies@FreeBSD.ORG, keith@cydonia.net Subject: Re: Tape Backup Message-ID: <199912070112.RAA45807@pau-amma.whistle.com> In-Reply-To: <Pine.LNX.4.04.9912061305110.13142-100000@mail.cydonia.net>
next in thread | previous in thread | raw e-mail | index | archive | help
>Date: Mon, 6 Dec 1999 13:34:14 -0800 (PST) >From: <keith@cydonia.net> >In need of some understanding/help. When installing a tape backup system. >Is it important to have compatability? Hmmm.... >I mean, does the system see it as a simple IDE/SCSI device >and not realy care what brand/model of tape backup system is?? The tape drive would usually be a "simple IDE/SCSI device" -- well, it has been in all the systems I've used (over the last 30 years). >Does the OS have to make a file system on the tape or is that a function >of the tape drive itself? Generally, tape devices do not contain "file systems," since that implies a degree of random access that a tape would require far too much latency to support. Further, tape drives are usually designed in such a way that once data has been written to the tape in a given place, you can't read data from "beyond" that point in the tape. (DECtapes are a little different, I understand....) Basically, a tape device usually acts as a device to which a stream of byte may be written or from which a stream of byte may be read. Put another way, it's a sequential (vs. random-access) device. >I'm going to be useing dump in FreeBSD >to do the backups "dump" is a program that reads a filesystem and generates a "stream of bytes"; its output can be assigned to "standard output" (and thus suitable for the input to a pipeline, for example, as well as writing to a sequential device, such as tape). >and don't realy have a good understanding of how tape >devices work in FreeBSD. Pretty much as they do in most UNIX systems -- you can write sequential data to them and reasd sequential data from them. There are conventions for writing "file marks" when a file is closed after having been opened for writing; that's how multiple files can be written to a single tape. >It's my understanding that there realy doesn't >need to be any real compatability becouse FreeBSD will just comunicate to >the device and the device takes care of the actual writing it in the >proper format on the tape no real need for a "driver" for a specific tape >device.. Thanks for any help. Not sure how you're intending to use the word "compatability" up there. The driver usually just treats the tape drive as a generic device, though -- as opposed, for example, to the way Ethernet NICs are handled, or SCSI host adapters. Cheers, david -- David Wolfskill dhw@whistle.com UNIX System Administrator voice: (650) 577-7158 pager: (888) 347-0197 FAX: (650) 372-5915 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-newbies" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199912070112.RAA45807>