Member Avatar for mukh mukherjee

I replaced a Quantum IDE drive in my external Firewire enclosure. Under OX 10 Panther, I formatted this drive and lost darn near 40% of the advertized space. I know it's normal to lose some to overhead, but THAT much? Any ideas?

Details: Western Digital 200MB Caviar ATA-100 EIDE (typical PC drive-- ordered from Tigerdirect.com) Replaced similar EIDE drive in a Firewire enclosure.

Formats out at: 128MB under Panther.

Thanks for any wisdom on this!

-Mukh

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The most likely cause is the FireWire enclosure’s ATA-to-FireWire bridge hitting the old 28-bit LBA limit (the “137 GB barrier”), not Panther or HFS+. That bridge can present a 200 GB (decimal) disk as only ~128 GiB visible to the OS. The decimal-vs-binary labeling used by drive makers explains only a small part of the gap; a true 40% loss points to the bridge chip or firmware.

The technical root: 28-bit LBA tops out at about 137.4 billion bytes (reported as ~128 GiB). Drives larger than that require 48-bit LBA support in the controller/bridge. See the Wikipedia notes on the and logical block addressing for background.

Quick checks to run on Panther:

diskutil list
diskutil info /dev/diskN   # replace diskN with the device from diskutil list
system_profiler SPFireWireDataType

Use System Profiler (FireWire section) to note the enclosure vendor/model/firmware string. If the bridge model is old, look for firmware updates from the enclosure maker or for documentation saying “48-bit LBA” or “supports >137 GB”.

Practical fixes: try the drive in another (newer) enclosure or attach it internally to a PC/Mac to confirm full capacity. If firmware is unavailable, replace the enclosure or use a PCI ATA/SATA controller that supports 48-bit LBA. As a short-term workaround you can partition the disk into slices <=137 GB each. Always back up data before repartitioning or flashing firmware.

Notes tied to earlier replies: was correct to point at the enclosure/controller; and ’s suspicion about a 128 GB cutoff is consistent with the LBA limit; and ’s reminder that OS X itself supports very large volumes is also applicable — the problem is the bridge.

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Member Avatar for Kezz

Hmm...
that shouldn't happen. I'd expect a 200 Gb (I assume you mean Gb not Mb) to leave you with well over 180 Gb free space.
Maybe Panther can't handle more than 128 Gb pr unit??
Anyone know about limitations on this ?

Member Avatar for digger

Hmm...
that shouldn't happen. I'd expect a 200 Gb (I assume you mean Gb not Mb) to leave you with well over 180 Gb free space.
Maybe Panther can't handle more than 128 Gb pr unit??
Anyone know about limitations on this ?

I've heard on other forums that you should partition to 128 gig as this is the limit under OS X. Maybe those better informed than myself can offer an explanation for this.

Member Avatar for kc0arf

Hello,

Apple's article says that it should handle 4 terabytes.

The thing though is that the partions become very unmanagable. If something goes wrong, how do you backup such a large volume?

I like to see multiple partitions on big disks, just to break them up, and keep them managable. I like making 3 partitions on my systems: 1 for the system files, a second for the applications, and a third for all the data. Then, I backup the data partitions, and go about my day.

Christian

Member Avatar for yellow

This is not a limit of OS X or HFS+.

It's quite possible that the ATA controller in your firewire enclosure is old. There is a limit on how large a drive they could handle. Newer ATA/5+ can handle volumes larger then 128GB (or 137GB).

Try a newer enclosure, our get a PCI ATA/6 card for inside your Mac and reformt to the proper size (186.2GB).

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