A single particle of Autographa californica nuclear polyhedrosis virus has a mass of about 1.5 femtograms, and its genome is 128 kilobases. If my calucaltions are right, you could store 1PB in 100 milligrams of virus particles. This was the only virus I've managed to find both figures for, so this result can probably be improved. For what I know, viruses can survive pretty harsh conditions, and this is a DNA virus, and DNA has two strands, so you're basically getting a RAID1. And it's the most popular data storage format on this planet.
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A single particle of Autographa californica nuclear polyhedrosis virus has a mass of about 1.5 femtograms, and its genome is 128 kilobases. If my calucaltions are right, you could store 1PB in 100 milligrams of virus particles. This was the only virus I've managed to find both figures for, so this result can probably be improved. For what I know, viruses can survive pretty harsh conditions, and this is a DNA virus, and DNA has two strands, so you're basically getting a RAID1. And it's the most popular data storage format on this planet.