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author | ru <ru@FreeBSD.org> | 2003-06-28 23:53:39 +0000 |
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committer | ru <ru@FreeBSD.org> | 2003-06-28 23:53:39 +0000 |
commit | 348e423dd913fabaea56f15eecca3d155723ee08 (patch) | |
tree | 119cebb3a669617b213ec04fe871163ae082cfb1 /share/man/man4/sa.4 | |
parent | e4f0eb6b17525e227a1bc1d660ab253005530425 (diff) | |
download | FreeBSD-src-348e423dd913fabaea56f15eecca3d155723ee08.zip FreeBSD-src-348e423dd913fabaea56f15eecca3d155723ee08.tar.gz |
Hiten's patchset for section four manpages, slightly edited by me.
Diffstat (limited to 'share/man/man4/sa.4')
-rw-r--r-- | share/man/man4/sa.4 | 55 |
1 files changed, 35 insertions, 20 deletions
diff --git a/share/man/man4/sa.4 b/share/man/man4/sa.4 index 9bf36f0..529bb46 100644 --- a/share/man/man4/sa.4 +++ b/share/man/man4/sa.4 @@ -57,11 +57,13 @@ The driver is based around the concept of a .Dq Em mount session , which is defined as the period between the time that a tape is -mounted, and the time when it is unmounted. Any parameters set during +mounted, and the time when it is unmounted. +Any parameters set during a mount session remain in effect for the remainder of the session or until replaced. The tape can be unmounted, bringing the session to a -close in several ways. These include: +close in several ways. +These include: .Bl -enum .It Closing a `rewind device', @@ -112,16 +114,17 @@ or block-size modes. Most .Tn QIC Ns -type devices run in fixed block-size mode, where most nine-track tapes and -many new cartridge formats allow variable block-size. The difference -between the two is as follows: +many new cartridge formats allow variable block-size. +The difference between the two is as follows: .Bl -inset .It Variable block-size: Each write made to the device results in a single logical record -written to the tape. One can never read or write +written to the tape. +One can never read or write .Em part of a record from tape (though you may request a larger block and read -a smaller record); nor can one read multiple blocks. Data from a -single write is therefore read by a single read. +a smaller record); nor can one read multiple blocks. +Data from a single write is therefore read by a single read. The block size used may be any value supported by the device, the .Tn SCSI @@ -136,19 +139,23 @@ but it was never read, then the next process to read will immediately hit the file mark and receive an end-of-file notification. .It Fixed block-size: Data written by the user is passed to the tape as a succession of -fixed size blocks. It may be contiguous in memory, but it is +fixed size blocks. +It may be contiguous in memory, but it is considered to be a series of independent blocks. One may never write -an amount of data that is not an exact multiple of the blocksize. One -may read and write the same data as a different set of records, In -other words, blocks that were written together may be read separately, +an amount of data that is not an exact multiple of the blocksize. +One may read and write the same data as a different set of records. +In other words, blocks that were written together may be read separately, and vice-versa. .Pp If one requests more blocks than remain in the file, the drive will -encounter the file mark. Because there is some data to return (unless +encounter the file mark. +As there is some data to return (unless there were no records before the file mark), the read will succeed, -returning that data, The next read will return immediately with a value -of 0. (As above, if the file mark is never read, it remains for the next +returning that data. +The next read will return immediately with a value +of 0. +(As above, if the file mark is never read, it remains for the next process to read if in no-rewind mode.) .El .Sh FILE MARK HANDLING @@ -156,15 +163,19 @@ The handling of file marks on write is automatic. If the user has written to the tape, and has not done a read since the last write, then a file mark will be written to the tape when the device is -closed. If a rewind is requested after a write, then the driver +closed. +If a rewind is requested after a write, then the driver assumes that the last file on the tape has been written, and ensures -that there are two file marks written to the tape. The exception to +that there are two file marks written to the tape. +The exception to this is that there seems to be a standard (which we follow, but don't understand why) that certain types of tape do not actually write two file marks to tape, but when read, report a `phantom' file mark when the -last file is read. These devices include the QIC family of devices. +last file is read. +These devices include the QIC family of devices. (It might be that this set of devices is the same set as that of fixed -block devices. This has not been determined yet, and they are treated +block devices. +This has not been determined yet, and they are treated as separate behaviors by the driver at this time.) .Sh IOCTLS The @@ -210,13 +221,17 @@ None. .Sh SEE ALSO .Xr mt 1 , .Xr scsi 4 -.Sh HISTORY +.Sh AUTHORS +.An -nosplit The .Nm driver was written for the .Tn CAM .Tn SCSI -subsystem by Justin T. Gibbs and Kenneth Merry. +subsystem by +.An Justin T. Gibbs +and +.An Kenneth Merry . Many ideas were gleaned from the .Nm st device driver written and ported from |