exnirad@brolga.cc.uq.oz.au (Nirad Sharma) (04/08/91)
What exactly is the meaning of "blocking" with reference to dd, tar, cpio etc ? Does it have something to do with checksumming ? What are the advantages of larger blocks as opposed to smaller blocks ? Many questions which I hope some guru can adequatly explain to me. Thanks Nirad Sharma (exnirad@brolga.cc.uq.oz.au) Phone : (61 7) 365 7575 Systems Programmer Fax : (61 7) 870 5080 Continuing Education Unit The University of Queensland AUSTRALIA -- Nirad Sharma (exnirad@brolga.cc.uq.oz.au) Phone : (61 7) 365 7575 Systems Programmer Fax : (61 7) 870 5080 Continuing Education Unit The University of Queensland
cpcahil@virtech.uucp (Conor P. Cahill) (04/08/91)
exnirad@brolga.cc.uq.oz.au (Nirad Sharma) writes: >What exactly is the meaning of "blocking" with reference to dd, tar, cpio >etc ? Does it have something to do with checksumming ? What are the advantages >of larger blocks as opposed to smaller blocks ? Blocking deals with the size of buffer the programs will use for io. This is important for two reasons. 1. performance. Generally a bigger block size will have better performance. However, this varies from device to device and the only way to know is by experimentation. 2. hardware. Some hardware (especially 9-track tape drives) write data to the device with the same blocking factor that is used by the program. On these devices, the correct way to read the data is with a block size that is at least as big as that used to write the tape. The blocking in the commands you listed has nothing to do with checksumming since none of those utilities perform checksumming (or CRCing). -- Conor P. Cahill (703)430-9247 Virtual Technologies, Inc. uunet!virtech!cpcahil 46030 Manekin Plaza, Suite 160 Sterling, VA 22170