USB disk size limits

[ctday]

Do the various Pi models have upper limits on the size of an external disk they can handle on USB?

[W. H. Heydt]

The only constraint is on how much power the external HDD requires. If it has its own power supply, there is no limit. If it has to be powered by the Pi, then the max 1.2A combined for all USB devices applies.

The EXT4 file system (used for root) can handle orders of magnitude more space than any existing HDD. If drives ever get to big for EXT4 (or what ever file system may be in use by that time), then it could be partitioned. The unix/Linux file system can span physical devices.

[ctday]

Thanks, that's what I thought. I'm having trouble with a 1TB SSD that keeps winding up corrupted and was hoping for an easy answer.

[W. H. Heydt]

Thanks, that's what I thought. I'm having trouble with a 1TB SSD that keeps winding up corrupted and was hoping for an easy answer.

Well...capacity certainly isn't the problem. Some SSDs have rather oddly high power requirements, though. Check the specifications on your drive. Something else to check is your USB to SATA adapter as not all of them play well with Pis. Also...be sure to shut down the system properly. While SSDs tend to have better controllers than SD cards or USB sticks, they still need at least a little time to flush their internal caches before be powered down.

There are posters to these forums that have reported using drives up to at least 2TB successfully. I've only used 60GB SSDs and a 314GB HDD, but none of them have given me any problems.

[LTolledo]

For me, I successfully USB booted the RPi (3B and 3B+) using the following drives

1. 2TB Seagate Barracuda HDD, 2,5"
2. 2TB Seagate FireCuda HDD, 2.5"
3. 1TB Marshall HDD, 2.5"
4. 240GB SanDisk SSD Plus SSD
5. 120GB Crucial BX500 SSD
6. 60GB Sunbow X3 SSD
7. 60GB KinDian KD-M200 mSATA (in Eluteng mSATA to USB3.0 case/adapter, for my piTop RPi3B setup)
8. 250GB DeskStar HDD, 3.5" (in self powered SATA to USB2.0 HDD case, HDD partitioned with EXT4 /root and NTFS /media/pi/HDD in same drive)

Am currently getting the 2.5" 4TB WD HDD for my RPi2B NAS, but will test it first for native USB boot on a RPi3B

for 1 to 6 above the adapters used are Eluteng Black SATA to USB3.0 adapter, and Inateck UA1003 SATA to USB3.0 adapter. May test other adapter cables that I fancy...next week

[fbe]

Am currently getting the 2.5" 4TB WD HDD for my RPi2B NAS, but will test it first for native USB boot on a RPi3B

You should be aware that MBR partitioning allows partition size up to 2TB. So even if it boots from your HDD you won't like it.

[andrum99]

Am currently getting the 2.5" 4TB WD HDD for my RPi2B NAS, but will test it first for native USB boot on a RPi3B

You should be aware that MBR partitioning allows partition size up to 2TB. So even if it boots from your HDD you won't like it.

There is an easy solution to that one - just use btrfs. It can use the entire disk without needing a partition table, although you would still need a partition table on the hard disk to boot from it. I believe GUID partition tables are supported for booting now as well, which removes the 2TB barrier completely.

[cspan]

For me, I successfully USB booted the RPi (3B and 3B+) using the following drives

1. 2TB Seagate Barracuda HDD, 2,5"
...

I haven't found HDD to spin up fast enough, even with the extended timeout set. I'm curious if you ever encountered that issue and if so, how you overcame it.

Mine were old 3.5" internal drives. Both using a USB docking station with its own power supply. A couple times it booted, but usually it would timeout. I had hoped to overcome it simply by powering on the docking station a few seconds prior to the Pi. However, the drive really didn't begin to spin up until the Pi was turned on, so that idea didn't pan out.

I have booted from USB "thumb" drives fine, but I like external HDD for big long-term storage. I have a couple USB-powered WD and Seagate external HDD that I like for that. But I've not tried them yet for Pi booting. I was concerned they'd be too big a power draw, but they do run fine when connected to an already-running Pi. They're readable.

[Imperf3kt]

Thanks, that's what I thought. I'm having trouble with a 1TB SSD that keeps winding up corrupted and was hoping for an easy answer.

Just to be sure, as it is a possibility, but you are positive it's not a fake? Are you sure the capacity is as it claims?

[LTolledo]

As mentioned by fbe for boot disk the max limit will most probably be 2TB.
its dictated by MBR partition limitations

I did tried booting from a 4TB drive, while it did boot, it was quite dismal as I cannot expand the file system, and ran to lots of troubles.

for data drive, it will be due to Linux limitation...

initially formatting the HDD with GPT will always revert back to MBR during raspbian image flashing by Etcher
unless the raspbian image flashing uses GPT instead of MBR we're all stuck to max 2TB.