Date: Thu, 26 Dec 1996 12:23:41 -0800 From: Julian Elischer <julian@whistle.com> To: Joerg Wunsch <joerg_wunsch@uriah.heep.sax.de> Cc: FreeBSD-current users <freebsd-current@freebsd.org> Subject: Re: DAT: reading with blocksize=256K Message-ID: <32C2DECD.41C67EA6@whistle.com> References: <199612261923.UAA27137@uriah.heep.sax.de>
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J Wunsch wrote: > > As Julian Elischer wrote: > > > the drive is in fixed block mode. > > in FIXED block mode what is actually written to tape is fixed blocks > > and many are written at a time for a large read/write > > But, you can't do 1 MB fixed blocks, right? :-) > no, but if you do a write of a 1MB block (e.g. dd bs=1M), physio will do 16 writes of 64K which will each be written as 64 x 1K blocks onto the media. This appears on tape as 1024 x 1K blocks which is indistinguishable from 1020 x 1K blocks written in one hit by (say) and SGI. and you can read the data back using (say) 4K reads in which case you'll get 4 1K blocks at each read, and you will get valid data for 256 reads.
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