Date: Fri, 11 Jan 2013 21:14:35 -0500 (EST) From: Diane Bruce <db@db.net> To: FreeBSD-gnats-submit@freebsd.org Subject: docs/175226: obsolete section on tapes in handbook Message-ID: <20130112021435.E120C1CCDF@night.db.net> Resent-Message-ID: <201301120220.r0C2K0rk035818@freefall.freebsd.org>
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>Number: 175226
>Category: docs
>Synopsis: obsolete section on tapes in handbook
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-doc
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: doc-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Jan 12 02:20:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Diane Bruce
>Release: FreeBSD 9.0-RELEASE amd64
>Organization:
Do I have to have any?
>Environment:
System: FreeBSD night.db.net 9.0-RELEASE FreeBSD 9.0-RELEASE #11: Sat Jun 30 08:32:31 EST 2012 root@night.db.net:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
>How-To-Repeat:
>Fix:
Index: en_US.ISO8859-1/books/handbook/disks/chapter.xml
===================================================================
--- en_US.ISO8859-1/books/handbook/disks/chapter.xml (revision 40568)
+++ en_US.ISO8859-1/books/handbook/disks/chapter.xml (working copy)
@@ -2085,234 +2085,77 @@
<indexterm><primary>tape media</primary></indexterm>
- <para>The major tape media are the 4mm, 8mm, QIC, mini-cartridge
- and DLT.</para>
+ <para>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. Nevertheless
+ FreeBSD will support any tape drive that uses SCSI such as LTO and
+ older devices such as DAT. There is limited support for SATA/USB tape
+ as well.
+ </para>
- <sect2 id="backups-tapebackups-4mm">
- <title>4mm (DDS: Digital Data Storage)</title>
+ <sect2 id="backups-tapebackups-sa0">
+ <title>Tape drives/serial access</title>
<indexterm>
- <primary>tape media</primary>
- <secondary>DDS (4mm) tapes</secondary>
+ <primary>tape drives</primary>
</indexterm>
- <indexterm>
- <primary>tape media</primary>
- <secondary>QIC tapes</secondary>
- </indexterm>
- <para>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.</para>
- <para>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.</para>
-
- <para>The DDS-3 standard now supports tape capacities up to
- 12 GB (or 24 GB compressed).</para>
-
- <para>4mm drives, like 8mm drives, use helical-scan. All the
- benefits and drawbacks of helical-scan apply to both 4mm and
- 8mm drives.</para>
-
- <para>Tapes should be retired from use after 2,000 passes or 100
- full backups.</para>
+ <para>FreeBSD uses the sa(4) driver, providing <devicename>/dev/sa0</devicename>,
+ <devicename>/dev/nsa0</devicename> and <devicename>/dev/esa0</devicename>.
+ In normal use only <devicename>/dev/sa0</devicename> is needed.
+ <devicename>/dev/nsa0</devicename> is the same
+ physical drive as <devicename>/dev/sa0</devicename> but does
+ not rewind the tape when a file is written to the tape and
+ this enables more than one backup to be done on a tape.
+ <devicename>/dev/esa0</devicename> Ejects the tape after
+ a close if applicable.
+ </para>
</sect2>
- <sect2 id="backups-tapebackups-8mm">
- <title>8mm (Exabyte)</title>
+ <sect2>
+ <title id="Using-mt">Using mt(1) to control the tape drive</title>
<indexterm>
<primary>tape media</primary>
- <secondary>Exabyte (8mm) tapes</secondary>
+ <secondary>mt</secondary>
</indexterm>
- <para>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.</para>
-
- <para>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.</para>
-
- <para>The Exabyte <quote>Mammoth</quote> model supports
- 12 GB on one tape (24 GB with compression) and costs
- approximately twice as much as conventional tape
- drives.</para>
-
- <para>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.</para>
+ <para>mt(1) is the FreeBSD 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.
+ </para>
+ <para>For example you have already written several backups to the tape
+ and you wish to save the first 3 backups without overwriting them.
+ <screen>mt -f <devicename>/dev/nsa0</devicename> fsf 3</screen>
+ </para>
</sect2>
- <sect2 id="backups-tapebackups-qic">
- <title>QIC</title>
+ <sect2>
+ <title id="Using-tar-on-tape">Using tar(1) to read/write backups on tape</title>
- <indexterm>
- <primary>tape media</primary>
- <secondary>QIC-150</secondary>
- </indexterm>
-
- <para>QIC-150 tapes and drives are, perhaps, the most common
- tape drive and media around. QIC tape drives are the least
- expensive <quote>serious</quote> 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
- <emphasis>most</emphasis> 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).</para>
-
- <para>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.</para>
-
- <para>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).</para>
-
- <para>Tapes should be retired from use after 5,000
- backups.</para>
+ <para>An example of a simple backup using tar(1) and a tape drive.
+ <screen>tar cv <filename>file</filename></screen>
+ As the default tape drive is <devicename>/dev/sa0</devicename>
+ there is no need to specify it.
+ To specify a specific tape deivce from the command line.
+ <screen>tar cvf <devicename>/dev/sa1</devicename><filename>dir</filename></screen>
+ </para>
+ <para>Typical use to recover files backed up with tar from a tape.
+ <screen>tar xvf <devicename>/dev/sa0</devicename></screen>
+ </para>
</sect2>
-
- <sect2 id="backups-tapebackups-dlt">
- <title>DLT</title>
-
- <indexterm>
- <primary>tape media</primary>
- <secondary>DLT</secondary>
- </indexterm>
-
- <para>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 <quote>hook</quote> 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.</para>
-
- <para>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.</para>
-
- <para>With compression, DLT Type IV format supports up to
- 70 GB capacity.</para>
-
- <para>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.</para>
- </sect2>
-
+
<sect2>
- <title id="backups-tapebackups-ait">AIT</title>
+ <title id="Using-dump-on-tape">Using restore(8)/dump(8) to read/write backups on tape</title>
- <indexterm>
- <primary>tape media</primary>
- <secondary>AIT</secondary>
- </indexterm>
-
- <para>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 <application>SAMS:Alexandria</application> 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.</para>
-
- <para>Libraries like this cost in the region of $20,000, pricing
- them a little out of the hobbyist market.</para>
+ <para>An example of a simple backup using dump(8) and a tape drive.
+ <screen>dump -0u -f <devicename>/dev/nsa0</devicename> <filename>/usr</filename></screen>
+ </para>
+ <para>Typical use to recover files backed up with dump(8) from a tape.
+ <screen>restore -f <devicename>/dev/nsa0</devicename></screen>
+ </para>
</sect2>
- <sect2>
- <title>Using a New Tape for the First Time</title>
-
- <para>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:</para>
-
- <screen>sa0(ncr1:4:0): NOT READY asc:4,1
-sa0(ncr1:4:0): Logical unit is in process of becoming ready</screen>
-
- <para>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:</para>
-
- <itemizedlist>
- <listitem>
- <para><command>mt fsf 1</command> causes the tape drive to
- write an Identifier Block to the tape.</para>
- </listitem>
-
- <listitem>
- <para>Use the front panel button to eject the tape.</para>
-
- <para>Re-insert the tape and <command>dump</command> data to
- the tape.</para>
-
- <para><command>dump</command> will report
- <errorname>DUMP: End of tape detected</errorname> and the
- console will show: <errorname>HARDWARE FAILURE info:280
- asc:80,96</errorname>.</para>
-
- <para>rewind the tape using:
- <command>mt rewind</command>.</para>
-
- <para>Subsequent tape operations are successful.</para>
- </listitem>
- </itemizedlist>
- </sect2>
</sect1>
<sect1 id="backups-floppybackups">
>Release-Note:
>Audit-Trail:
>Unformatted:
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