Up to Storage Pod 5.0 they used 45 per 4U, 6.0 was 60 indeed but it was hanging out from the rack so it is understandable no major OEM has a chassis like that.

Up to Storage Pod 5.0 they used 45 per 4U, 6.0 was 60 indeed but it was hanging out from the rack so it is understandable no major OEM has a chassis like that. 52 serviceable drives is not bad at all.