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I Recently bought a 2Tb external drive and configured time machine on my OS X 10.6.8 iMac. It started by making a full backup (approximately 1.6 Tb). Fine. I see a series of hourly incremental backups have run (a few hundred Mb each) A week goes by. All is good I have about 400Gb free on the backup disk. Suddenly it wants to make another 1.6 TB full backup. Disk full error. This implies that weekly (and I now assume, monthly) backups are not incremental. Is that correct?