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Full Discussion: Optimal block size in dd
Operating Systems HP-UX Optimal block size in dd Post 302429430 by methyl on Monday 14th of June 2010 11:53:02 AM
Old 06-14-2010
Even with "conv=sync" a "dd" to tape should be of a structured file. My "cpio" and "tar" won't do files above 2Gb. We don't know what O/S version you have.
The optimum block size to tape depends on the properties of the tape deck and driver.
May be better to use proper backup software, checking whether it will handle very large files of 8Gb or more.
 

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MT(1)							      General Commands Manual							     MT(1)

NAME
mt - magnetic tape manipulating program SYNOPSIS
mt [ -f tapename ] command [ count ] DESCRIPTION
Mt is used to give commands to a magnetic tape drive. If a tape name is not specified, the environment variable TAPE is used; if TAPE does not exist, mt uses the device /dev/rmt12. Note that tapename must reference a raw (not block) tape device. By default mt performs the requested operation once. Operations may be performed multiple times by specifying count. The available commands are listed below. Only as many characters as are required to uniquely identify a command need be specified. eof, weof Write count end-of-file marks at the current position on the tape. fsf Forward space count files. fsr Forward space count records. bsf Back space count files. bsr Back space count records. rewind Rewind the tape (Count is ignored). offline, rewoffl Rewind the tape and place the tape unit off-line (Count is ignored). status Print status information about the tape unit. cacheon Enable the readahead/writebehind cache on the tape unit. cacheoff Turn off the readahead/writebehind cache on the tape unit. Mt returns a 0 exit status when the operation(s) were successful, 1 if the command was unrecognized, and 2 if an operation failed. The cacheon and cacheoff commands currently only apply to the TMSCP driver and then only for certain drives such as the TU81+. No error is produced by the TMSCP driver if the cache commands are used. Other drivers will return an error code since they do not recognize the MTCACHE and MTNOCACHE functions codes. See mtio(4). FILES
/dev/rmt* Raw magnetic tape interface SEE ALSO
mtio(4), tmscp(4), dd(1), ioctl(2), environ(7) 4th Berkeley Distribution December 22, 1995 MT(1)
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