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2TB SATA III HDD via USB 3.0/2.0 external enclosure 500GB SATA II HDD via USB 2.0 external enclosure Both hooked up to Raspberry Pi, no hubs or other USB devices being used

Both disks are mostly empty. Since USB 2.0 is supposed to be 480Mbit/s, and the drives can probably do 50-100MB/s reading/writing. I would expect at least 10-20MB/s transfer speed, but I'm only getting around 5MB/s. Any ideas?

Seán Hayes
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  • Are you doing any sort of concurrent reading/writing to either of the drives while using it? Is it possible either drive is highly fragmented? Are the usb and sata cables in good shape? (Damaged cables lead to lots of signal loss and errors.) Anything in /var/log/syslog or /var/log/dmesg? – Stephan Feb 06 '13 at 03:15
  • No other reading/writing is being done. Both drives were mostly empty so I don't think they'd be fragmented. Both external enclosures are brand new, so there's no cable problems. demsg looked fine, as far as I can tell both enclosures are connected via USB 2.0 high speed. I just checked syslog and noticed 'NTFS-fs error (device sda1): ntfs_readdir(): Directory index record with vcn 0x0 is corrupt. Corrupt inode 0xd0f2. Run chkdsk.' (FYI, I finished copying the 500GB disk and am now copying a mostly full 500GB disk). I'll try chkdsk and see if it helps. – Seán Hayes Feb 06 '13 at 23:50
  • The NTFS-fs error sounds like a clue to me; lemme know if chkdsk helps! – Stephan Feb 07 '13 at 00:52
  • I fixed the chkdsk error but it's still only around 5MB/s. – Seán Hayes Feb 07 '13 at 01:20
  • I'd be suspect of one of the drives being defective at this point; if you have a different hard drive to try, that would rule this out. – Stephan Feb 07 '13 at 01:29
  • Writing to my 2TB drive from my laptop goes 125MB/s. I'll test reading from the 500GB drive. – Seán Hayes Feb 07 '13 at 04:34
  • Copying (reading) from the 500GB drive to my laptop only goes about 17MB/s. From what I've read it looks like ntfs just works really slowly on Linux. I'll try attaching the ntfs drive to Windows and transferring over the network. – Seán Hayes Feb 07 '13 at 05:46
  • No improvement over my LAN. 'sudo cat /dev/sdb1 | pv -r > /dev/null' does show about 20MB/s reading from the 500GB drive, so using the other USB drive and some rsync overhead must be slowing things down. – Seán Hayes Feb 07 '13 at 07:21
  • Am running out of ideas myself here, sorry. If it's only reading the raw disk at about 20MB/s, then somethings obviously gummed up. You don't mention the hard drive model, but especially of interest is if it is a 5200 rpm, how old it is, and if you're 100% sure the power supply is not faulty. At least it seems to be a hardware issue. – Stephan Feb 07 '13 at 11:08

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