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   <TITLE>Freesoft Linux FAQ -- 关于磁带机密度的问题</TITLE>
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mirnshi wrote:

<P>> 我的8毫米磁带机不能正确识别磁带的密度,怎么办? 如何正确设置磁带机的
<BR>> 密度.
<BR>>
<BR>> 问题的由来:
<BR>> 我有一些在SUN工作站上用8mm磁带备份的数据文件,我想在微机上的
<BR>> linux(rd5)下读出来,微机的磁带机是EXAByte 8505, 当时用tar命令或dd命令
<BR>> 时都报错.
<BR>> $ tar&nbsp; tvf&nbsp; /dev/st0
<BR>> st0: Incorrect block size
<BR>> tar: Read error on /dev/st0:Input/Output error

<P>这不是密度的问题而是块尺寸问题。你原先设置的尺寸是多少就用mt命令把磁带机的块尺寸设为多少。
<BR>用man mt看具体的命令格式，好象是用setblk子命令。
<BR>密度也可以用mt命令来设。

<P>另外tar命令也有块尺寸的设置问题。GNU tar的默认值好象是20*512，你原来
<BR>的tar用多少？用tar -b NN指定tar的块储存。

<P>min
<BR>&nbsp;

<P>mirnshi wrote:

<P>> Mr. Gong:
<BR>>
<BR>> I use default block size on SUN_ws.And SUN default block size also
is 20
<BR>> I can tar 1/4 tape that backup from SUN_ws.

<P>20 must be the default tar block size which means 20*512 not 20 bytes.There
is
<BR>another block size, that is, the physical block size of the tape device.

<P>For saving tape I used physical tape block size of 16384 to write our
DDS-2
<BR>tape. When it was read by a HP-UX server without specifying the physical
<BR>block size the result was like what you mentioned. When the physical
block
<BR>size of the tape was adjusted to the physical block size of the recorded
tape
<BR>the problem was solved. So, try to find out the physical block size
of your tape
<BR>and adjust the Linux tape device block size with mt command it will
be OK.

<P>> I also used dd, it was also error. It seems that dd can read any block
size
<BR>> tape.

<P>So, your TAPE PHYSICAL BLOCK SIZE in NOT correct.

<P>> WHY?
<BR>>
<BR>> BTW, my tape is 5GB.

<P>Please read the man page and other docs of mt.

<P>>
<BR>>
<BR>> mirnshi

<P>Good luck.

<P>min
<BR>&nbsp;

<P>Linux下对磁带机的物理块默认设置为512 bytes并且不自动支持可变块长. 你可
<BR>用下述命令设置为支持可变块:

<P>mt setblk 0

<P>然后再用tar或dd就不会有问题. 但要注意做了上述设置后要重设为其它块大小
<BR>才能正确写带.
<BR>&nbsp;
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