I need to split a large stream of approx 600 GB that gets generated by Solaris' zfs send command. I could try the whole chain with a big enough file but I don't see how the zfs command could be the problem as it only generates a stream.
These two commands work as expected: # zfs send <backup> | wc gives the expected result, wc displays the full size of the backup, well beyond 140 GB, as I'm interested in the first 140 GB I think this is good. # cat /dev/zero | dd bs=512 count=293601280 | wc gives also expected results, dd reads exactly 293601280 blocks and wc sees 150323855360 characters, that is, 140 GB The problem comes when I combine the former part of the first command with the latter of the second, dd always reads short of the count value: # zfs send <backup> | dd bs=512 count=293601280 | wc 293590463+10817 records in 293590463+10817 records out Admittedly, this is Solaris' dd but when I pipe the stream through nc to an up-to-date Linux box and do the dd there, I also get short reads on the last block. I haven't tried BSD dd yet. bs=512 is the last attempt I made but I've tried combinations of the bs and count parameters to no avail, nothing seems to work with the 600 GB stream. I haven't tried bs=1 as I think it would take weeks to go through but maybe I'm wrong. If I try with smaller files, up to hundreds of MBs dd works fine, but I can't tell at what size it breaks or under which circumstances or why. I welcome any pointers at this time. Thanks, Lucia
