3TB hard drive shows only 800GB?!!

thesun · #1 24th June 2012, 01:43 AM

Hi, just got a Western Digital 3TB drive and have it hooked up via USB (one of those universal adapter things). I've done this before with a 2TB drive and had no issues, but this drive is showing up under Gparted and the Fedora 13 Disk Utility as having only 800GB.

I'm wondering if I just have a bum hard drive or if perhaps this is "800" due to some other reason, like maybe my system (Fedora 13) isn't able to see drives that large?

Anyone know of any way to confirm whether this is a hardware flaw before I drive all the way back to the store to get another one (only to have the same thing happen again)?

Thank you!

stevea · #2 24th June 2012, 04:48 AM

It' very odd. What does hdparm report in the drive ?

Doug G · #3 24th June 2012, 05:15 AM

Many usb external drive enclosures have a 2tb drive size limit. Verify your usb dock supports a 3tb disk.

george_toolan · #4 24th June 2012, 08:19 AM

The explanation is rather simple: the size is displayed modulo 2 TiB, so 3000 minus 2200 is 800 ;-)

The best way to avoid this is to buy an external 3 TiB drive.

thesun · #5 24th June 2012, 12:52 PM

I guess the question (having bought a 3TB internal drive) is how (if it's 3000-2200=800) to get it to properly recognize.

I can't imagine that all Linux users are stuck at a 2.2TB limit. Do I need to reformat with GUID?

I did not find much out there yet on the web about it, but surely a 3TB external usb drive is just a 3TB internal drive with an enclosure, no? Why would buying a 3TB external solve the problem...and couldn't that problem be solved with some formatting/tweaking and thus not need an enclosure?

Thanks for any and all help/suggestions!!!

marko · #6 24th June 2012, 01:06 PM

fdisk can't go above 2TB yet

Either partition into multiple partitions so none is bigger than 2TB or use
a GPT capable partition tool, 'parted' would work.

REF:
http://www.cyberciti.biz/tips/fdisk-...eater-2tb.html
http://www.webhostingskills.com/arti...than_2tb_linux

george_toolan · #7 24th June 2012, 01:09 PM

It has nothing to do with Linux when the USB chip in your enclosure only supports 2 TiB drives.

An external drive is an internal drive with a USB adapter chip with support for large drives and which pretends the drive has 4k sectors.

Go ahead and try to format the drive with a GPT, but you probably won't have much luck if the drive is only reported as 800 GB.

Code:

gdisk /dev/sdX

marko · #8 24th June 2012, 01:17 PM

Quote:

Originally Posted by george_toolan

It has nothing to do with Linux when the USB chip in your enclosure only supports 2 TiB drives.

An external drive is an internal drive with a USB adapter chip with support for large drives and which pretends the drive has 4k sectors.

Go ahead and try to format the drive with a GPT, but you probably won't have much luck if the drive is only reported as 800 GB.

Code:

gdisk /dev/sdX

But my point is that you can't just solve the problem by using a different enclosure, Linux fdisk can't fundamentally deal with > 2TB partitions. So after solving the enclosure problem he has to use gdisk or parted.

thesun · #9 24th June 2012, 02:43 PM

So if I'm understanding this right, even though I'm not using any kind of enclosure, the USB raw adapter (essentially a cable with a SCSI connector at one end and a USB plug at the other) is causing the problem. Parted isn't going to help me until I have a connection to the drive that can go above 2.2TB...yes?

There's almost no documentation with the adapter, but it does say "compatible with all 2.5 and 3.5 IDE and SATA drives."

I actually tried using parted prior to posting but it still showed only 800GBs. So if I'm understanding it right, first I need to get a different USB connector, then I need to use parted to format it, and then finally I should be able to see it as a full 3TB drive once that's done?

Thanks again for the help...this is a bit frustrating...drove an hour and a half to get the drive and could have come back with a 2TB one and saved myself the agony. It'd be great to get this working...

Magickman · #10 24th June 2012, 03:15 PM

I had the same problem with a Seagate 250 Gb drive. G-Parted reported it as 320 MB. I erased it, and still the same. Ran Seatools on it, and reset the drive for maximun space, and that did the trick. I use UBCD for this, a nice little set of tools for any hobbist.
http://www.ultimatebootcd.com/download.html

thesun · #11 24th June 2012, 03:19 PM

Magickman, from the sounds of what others are saying this is a different issue -- 250GB is a whole different ballgame, right? Or were there similar USB-related issues back when 250GB came out?

It sounds like there's a hardware-related limit of 2.2TB when using these USB connectors. I've ordered a different one that says it works up to 3TB, so hopefully when that comes the issue will be only a matter of formatting with parted (anyone, with "Gparted" work the same?)

Thanks!

smr54 · #12 24th June 2012, 04:00 PM

Please keep us posted. Annoying as it was for you, it might save someone else from having the same aggravation.

srs5694 · #13 24th June 2012, 04:17 PM

Quote:

Originally Posted by thesun

So if I'm understanding this right, even though I'm not using any kind of enclosure, the USB raw adapter (essentially a cable with a SCSI connector at one end and a USB plug at the other) is causing the problem. Parted isn't going to help me until I have a connection to the drive that can go above 2.2TB...yes?

Correct.

Quote:

There's almost no documentation with the adapter, but it does say "compatible with all 2.5 and 3.5 IDE and SATA drives."

Then either the adapter predates >2TiB drives or they lied.

Quote:

So if I'm understanding it right, first I need to get a different USB connector, then I need to use parted to format it, and then finally I should be able to see it as a full 3TB drive once that's done?

Correct.

Quote:

It sounds like there's a hardware-related limit of 2.2TB when using these USB connectors.

Correct. Doug G and george_toolan have been saying this quite explicitly all along. To further elaborate, many external interfaces have a 32-bit limit on their sector values. This means that they can handle up to 2^32 sectors. Given a standard sector size of 512 bytes, that works out to precisely 2 TiB (2.2 TB), so any disk over that value will not be fully usable. The interfaces tend to just drop the part of the sector values that go beyond 32 bits, which means you probably won't be able to access part of the disk, and the disk's size will be incorrectly reported as a sub-2TiB value.

The only way around this problem is to get an external enclosure/adapter that supports over-2TiB disks. Some do this by remapping the sectors into 4KiB sectors, which raises the limit to 16 TiB. Some may do it with 64-bit interfaces, but I'm not 100% positive that any do this.

Note that if you plan to move the disk between external and internal use, an adapter that re-maps sectors into 4KiB logical sectors will cause problems, since software will see the disk as having 512-byte sectors when the disk is attached internally and 4096-byte sectors when it's connected externally. This inconsistency will make the disk inaccessible using whichever method was not used to prepare it originally. This isn't normally a problem for an external enclosure, since those are generally used in a more-or-less permanent fashion; but it may be an issue for an external adapter, which is often used on a temporary basis. You've said you're using an adapter, so it's not clear to me what your long-term use plans are, and I thought this should be brought to your attention. If you plan to prepare the disk with the adapter and then move it inside a computer, your safest course of action is probably to move the disk straight into the computer and forget about using it with an external adapter first. Post back with details of your plans if you have unusual needs that involve swapping the disk between adapters.

thesun · #14 24th June 2012, 05:05 PM

@srs5694, thanks for the clarifications. I'm not planning to switch between internal and external use, just to have it on hand as an easily detachable backup drive. So probably my (on order) "<3TB OK" USB adapter will be all I need. Once that comes I'll follow up here with whether it worked (or not!) and possibly more questions. But this sounds clear enough. I'm glad I didn't drive all the way back to the store and swap the drive thinking it was faulty! Thanks (all) for the advice!

george_toolan · #15 24th June 2012, 05:57 PM

AFAIK all external drives use 4K sectors for compatibility reasons explained above.

Btw the 2 TiB limit can affect all sata host adapters and not just external sata to usb converter chips.

Can you test if the drives works internally or do you have a notebook computer?

If you have an empty 5,25" drive bay I would recommend a sata hot swap frame rather than placing the bare HDD on your table where it could fall off. Something like this one http://www.delock.de/produkte/G_4719...setLanguage=en