I am running Ubuntu 18.04 on an HP Spectre which has USB-C connectors. I have a Samsung T3 500G SSD which I wipe & then rewrite to back up my data from the SSD of the HP. Transfer speeds for sequential transfer for the T3 are quoted as over 400 Mb/s. However my transfer speed (non-sequential) is around 40 Mb/s. What causes the slowdown ?

  • How do you connect the backup SSD to the HP? Could be an older controller and thus limited in speed? – eblock Jan 4 '19 at 10:57
  • Could be many factors that affect it. But an order of magnitude slow down compared to sequential is not unheard of for an SSD. The way an SSD works is that random requests can be accessed at the same time as long as they don't share the same part of the SSD. This means the type of controller dictates whether you get an order of magnitude slow down or just maybe half speed compared to sequential. But assuming the controller is good my guess in the dark here is that your USB connection is limited in threats or requests somehow. – jdwolf Jan 4 '19 at 11:12
  • USB-C is also shared with Thunderbolt. If that SSD was meant to use Thunderbolt and the laptop doesn't support it on that port that might be it. Make sure you try all the USB-C ports. – jdwolf Jan 4 '19 at 11:13
  • Connection is either by USB-C to USB-C cable or by USB-C to USB3 cable. It doesn't seem to affect the transfer rate. – Chris Holmes Jan 4 '19 at 15:38

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