For quite a while, I used a 10,000 RPM, 18 GB SCSI drive in my SE/30. I also ran it with an extra fan for ventilation, and an extra power supply running said drive. Made a great AppleShare 3 server for my home network.
In theory, a Macintosh Plus running System 7.5.5 could in theory have a 2 TB volume size! (Note that with original HFS, you could only have 65,535 files, at a maximum file size of 2 GB, so in order to reach 2 TB, you'd have to have average 32 MB per file up to the 65k limit.) But if you had a SATA-to-SCSI adapter, you could throw up to 7 of the new 3 Terabyte drives onto a Mac Plus, and just use a a few partitions on each.
(Using, for example, you could use seven of these monsters to JBOD 8 drives each. Because you'd be connecting to a Narrow SCSI host, you'd only get to use 7 of these; each as a separate SCSI ID, each with 8 SCSI LUNs (1 for each drive; since Mac OS 7.5.5 can't handle volumes that large.) But eight 2 TB drives would still be 16 TB of drive space per device. Seven of these would be 112 TB. On a Mac Plus. Of course, if you actually wanted to get data *ON* them, you'd have to give up one of them for a SCSI Ethernet adapter, so only 96 TB. And while I'm thinking of this, you'd have to take into account that the maximum speed the Mac Plus could possibly write to them is 1.25 MB/s. So if you started writing to it right now, you'd finish up sometime in mid-April, 2013.)
In theory, a Macintosh Plus running System 7.5.5 could in theory have a 2 TB volume size! (Note that with original HFS, you could only have 65,535 files, at a maximum file size of 2 GB, so in order to reach 2 TB, you'd have to have average 32 MB per file up to the 65k limit.) But if you had a SATA-to-SCSI adapter, you could throw up to 7 of the new 3 Terabyte drives onto a Mac Plus, and just use a a few partitions on each.
(Using, for example, you could use seven of these monsters to JBOD 8 drives each. Because you'd be connecting to a Narrow SCSI host, you'd only get to use 7 of these; each as a separate SCSI ID, each with 8 SCSI LUNs (1 for each drive; since Mac OS 7.5.5 can't handle volumes that large.) But eight 2 TB drives would still be 16 TB of drive space per device. Seven of these would be 112 TB. On a Mac Plus. Of course, if you actually wanted to get data *ON* them, you'd have to give up one of them for a SCSI Ethernet adapter, so only 96 TB. And while I'm thinking of this, you'd have to take into account that the maximum speed the Mac Plus could possibly write to them is 1.25 MB/s. So if you started writing to it right now, you'd finish up sometime in mid-April, 2013.)