From owner-svn-doc-head@FreeBSD.ORG Fri Jan 18 01:17:05 2013 Return-Path: Delivered-To: svn-doc-head@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 17FB1ACE; Fri, 18 Jan 2013 01:17:05 +0000 (UTC) (envelope-from wblock@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:1900:2254:2068::e6a:0]) by mx1.freebsd.org (Postfix) with ESMTP id EF843172; Fri, 18 Jan 2013 01:17:04 +0000 (UTC) Received: from svn.freebsd.org ([127.0.1.70]) by svn.freebsd.org (8.14.5/8.14.5) with ESMTP id r0I1H4Em081684; Fri, 18 Jan 2013 01:17:04 GMT (envelope-from wblock@svn.freebsd.org) Received: (from wblock@localhost) by svn.freebsd.org (8.14.5/8.14.5/Submit) id r0I1H4J9081683; Fri, 18 Jan 2013 01:17:04 GMT (envelope-from wblock@svn.freebsd.org) Message-Id: <201301180117.r0I1H4J9081683@svn.freebsd.org> From: Warren Block Date: Fri, 18 Jan 2013 01:17:04 +0000 (UTC) To: doc-committers@freebsd.org, svn-doc-all@freebsd.org, svn-doc-head@freebsd.org Subject: svn commit: r40676 - head/en_US.ISO8859-1/books/handbook/disks X-SVN-Group: doc-head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-doc-head@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: SVN commit messages for the doc tree for head List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Jan 2013 01:17:05 -0000 Author: wblock Date: Fri Jan 18 01:17:04 2013 New Revision: 40676 URL: http://svnweb.freebsd.org/changeset/doc/40676 Log: Update the Using Tapes section to more closely reflect modern reality. Modified version of patch from PR. PR: docs/175226 Submitted by: Diane Bruce Modified: head/en_US.ISO8859-1/books/handbook/disks/chapter.xml Modified: head/en_US.ISO8859-1/books/handbook/disks/chapter.xml ============================================================================== --- head/en_US.ISO8859-1/books/handbook/disks/chapter.xml Thu Jan 17 22:52:01 2013 (r40675) +++ head/en_US.ISO8859-1/books/handbook/disks/chapter.xml Fri Jan 18 01:17:04 2013 (r40676) @@ -2085,233 +2085,93 @@ cd0: Attempt to query device size failed tape media - The major tape media are the 4mm, 8mm, QIC, mini-cartridge - and DLT. + Tape technology has continued to evolve but is less likely + to be used in a modern system. Modern backup systems tend to + use offsite combined with local removable disk drive + technologies. Still, FreeBSD will support any tape drive that + uses SCSI such as LTO and older devices such as DAT. There is + limited support for SATA and USB tape drives as well. - - 4mm (DDS: Digital Data Storage) + + Serial Access with &man.sa.4; - tape media - DDS (4mm) tapes + tape drives - - tape media - QIC tapes - - 4mm tapes are replacing QIC as the workstation backup - media of choice. This trend accelerated greatly when Conner - purchased Archive, a leading manufacturer of QIC drives, and - then stopped production of QIC drives. 4mm drives are small - and quiet but do not have the reputation for reliability that - is enjoyed by 8mm drives. The cartridges are less expensive - and smaller (3 x 2 x 0.5 inches, 76 x 51 x 12 mm) than 8mm - cartridges. 4mm, like 8mm, has comparatively short head life - for the same reason, both use helical scan. - - Data throughput on these drives starts ~150 kB/s, - peaking at ~500 kB/s. Data capacity starts at - 1.3 GB and ends at 2.0 GB. Hardware compression, - available with most of these drives, approximately doubles the - capacity. Multi-drive tape library units can have 6 drives in - a single cabinet with automatic tape changing. Library - capacities reach 240 GB. - - The DDS-3 standard now supports tape capacities up to - 12 GB (or 24 GB compressed). - - 4mm drives, like 8mm drives, use helical-scan. All the - benefits and drawbacks of helical-scan apply to both 4mm and - 8mm drives. - Tapes should be retired from use after 2,000 passes or 100 - full backups. + FreeBSD uses the &man.sa.4; driver, providing + /dev/sa0, + /dev/nsa0, and + /dev/esa0. In normal use, only + /dev/sa0 is needed. + /dev/nsa0 is the same physical drive + as /dev/sa0 but does not rewind the + tape after writing a file. This allows writing more than one + file to a tape. Using /dev/esa0 + ejects the tape after the device is closed, if + applicable. - - 8mm (Exabyte) - - - tape media - Exabyte (8mm) tapes - - - 8mm tapes are the most common SCSI tape drives; they are - the best choice of exchanging tapes. Nearly every site has an - Exabyte 2 GB 8mm tape drive. 8mm drives are reliable, - convenient and quiet. Cartridges are inexpensive and small - (4.8 x 3.3 x 0.6 inches; 122 x 84 x 15 mm). One downside of - 8mm tape is relatively short head and tape life due to the - high rate of relative motion of the tape across the - heads. - - Data throughput ranges from ~250 kB/s to - ~500 kB/s. Data sizes start at 300 MB and go up to - 7 GB. Hardware compression, available with most of these - drives, approximately doubles the capacity. These drives are - available as single units or multi-drive tape libraries with 6 - drives and 120 tapes in a single cabinet. Tapes are changed - automatically by the unit. Library capacities reach - 840+ GB. - - The Exabyte Mammoth model supports - 12 GB on one tape (24 GB with compression) and costs - approximately twice as much as conventional tape - drives. - - Data is recorded onto the tape using helical-scan, the - heads are positioned at an angle to the media (approximately 6 - degrees). The tape wraps around 270 degrees of the spool that - holds the heads. The spool spins while the tape slides over - the spool. The result is a high density of data and closely - packed tracks that angle across the tape from one edge to the - other. - - - - QIC + + Controlling the Tape Drive with + &man.mt.1; tape media - QIC-150 + mt - QIC-150 tapes and drives are, perhaps, the most common - tape drive and media around. QIC tape drives are the least - expensive serious backup drives. The downside - is the cost of media. QIC tapes are expensive compared to 8mm - or 4mm tapes, up to 5 times the price per GB data storage. - But, if your needs can be satisfied with a half-dozen tapes, - QIC may be the correct choice. QIC is the - most common tape drive. Every site has a - QIC drive of some density or another. Therein lies the rub, - QIC has a large number of densities on physically similar - (sometimes identical) tapes. QIC drives are not quiet. These - drives audibly seek before they begin to record data and are - clearly audible whenever reading, writing or seeking. QIC - tapes measure 6 x 4 x 0.7 inches (152 x - 102 x 17 mm). - - Data throughput ranges from ~150 kB/s to - ~500 kB/s. Data capacity ranges from 40 MB to - 15 GB. Hardware compression is available on many of the - newer QIC drives. QIC drives are less frequently installed; - they are being supplanted by DAT drives. - - Data is recorded onto the tape in tracks. The tracks run - along the long axis of the tape media from one end to the - other. The number of tracks, and therefore the width of a - track, varies with the tape's capacity. Most if not all newer - drives provide backward-compatibility at least for reading - (but often also for writing). QIC has a good reputation - regarding the safety of the data (the mechanics are simpler - and more robust than for helical scan drives). - - Tapes should be retired from use after 5,000 - backups. - - - - DLT + &man.mt.1; is the &os; utility for controlling other + operations of the tape drive, such as seeking through files on + a tape or writing tape control marks to the tape. - - tape media - DLT - + For example, the first three files on a tape can be + preserved by skipping past them before writing a new + file: - DLT has the fastest data transfer rate of all the drive - types listed here. The 1/2" (12.5mm) tape is contained in a - single spool cartridge (4 x 4 x 1 inches; 100 x 100 x 25 mm). - The cartridge has a swinging gate along one entire side of the - cartridge. The drive mechanism opens this gate to extract the - tape leader. The tape leader has an oval hole in it which the - drive uses to hook the tape. The take-up spool - is located inside the tape drive. All the other tape - cartridges listed here (9 track tapes are the only exception) - have both the supply and take-up spools located inside the - tape cartridge itself. - - Data throughput is approximately 1.5 MB/s, three - times the throughput of 4mm, 8mm, or QIC tape drives. Data - capacities range from 10 GB to 20 GB for a single - drive. Drives are available in both multi-tape changers and - multi-tape, multi-drive tape libraries containing from 5 to - 900 tapes over 1 to 20 drives, providing from 50 GB to - 9 TB of storage. - - With compression, DLT Type IV format supports up to - 70 GB capacity. - - Data is recorded onto the tape in tracks parallel to the - direction of travel (just like QIC tapes). Two tracks are - written at once. Read/write head lifetimes are relatively - long; once the tape stops moving, there is no relative motion - between the heads and the tape. + &prompt.root; mt -f /dev/nsa0 fsf 3 - AIT + Using &man.tar.1; to Read and + Write Tape Backups - - tape media - AIT - + An example of writing a single file to tape using + &man.tar.1;: - AIT is a new format from Sony, and can hold up to - 50 GB (with compression) per tape. The tapes contain - memory chips which retain an index of the tape's contents. - This index can be rapidly read by the tape drive to determine - the position of files on the tape, instead of the several - minutes that would be required for other tapes. Software such - as SAMS:Alexandria can operate - forty or more AIT tape libraries, communicating directly with - the tape's memory chip to display the contents on screen, - determine what files were backed up to which tape, locate the - correct tape, load it, and restore the data from the - tape. + &prompt.root; tar cvf /dev/sa0 file - Libraries like this cost in the region of $20,000, pricing - them a little out of the hobbyist market. + Recovering files from a &man.tar.1; archive on tape into + the current directory: + + &prompt.root; tar xvf /dev/sa0 - Using a New Tape for the First Time + Using &man.dump.8; and + &man.restore.8; to Create and Restore Backups - The first time that you try to read or write a new, - completely blank tape, the operation will fail. The console - messages should be similar to: + A simple backup of /usr with &man.dump.8;: - sa0(ncr1:4:0): NOT READY asc:4,1 -sa0(ncr1:4:0): Logical unit is in process of becoming ready + &prompt.root; dump -0aL -b64 -f /dev/nsa0 /usr - The tape does not contain an Identifier Block (block - number 0). All QIC tape drives since the adoption of QIC-525 - standard write an Identifier Block to the tape. There are two - solutions: + Interactively restoring files from a &man.dump.8; file on + tape into the current directory: - - - mt fsf 1 causes the tape drive to - write an Identifier Block to the tape. - - - - Use the front panel button to eject the tape. - - Re-insert the tape and dump data to - the tape. - - dump will report - DUMP: End of tape detected and the - console will show: HARDWARE FAILURE info:280 - asc:80,96. + &prompt.root; restore -i -f /dev/nsa0 + - rewind the tape using: - mt rewind. + + Other Tape Software - Subsequent tape operations are successful. - - + Higher-level programs are available to simplify tape + backup. The most popular are + AMANDA and + Bacula. These programs aim to make + backup easier and more convenient, or to automate complex + backups of multiple machines. The Ports Collection contains + both these and other tape utility applications.