>From the original report: "When the device is under load and more than 1 hardrive is acessed, the USB enclosure frequently restarts."
So this very much sounds like a hardware problem. UAS allows having multiple outstanding commands (read/write requests) and thus *actually* accessing multiple disks at once. If you disable UAS then there can be only 1 read *or* write requests be done at a time and only when that requests has fully completed, which requires 3 round-trips to the device, then the next request can be send. So, especially when accessing multiple drives (or a SSD) using the old mass-storage USB protocol is much much slower. The slowness has one advantage though, if only 1 thing is done at a time / only 1 drive accesses at a time, then much less power is consumed by the driver. Unfortunately this often causes people to believe that there is a bug in the UAS driver, where as the real problem is the power-supply of their disk enclosure not providing enough power. "the USB enclosure frequently restarts." is exactly what one would expect with brown-out (voltage level getting too low) issues like this. So I'm 90% sure that this an issue with the power-supply used to power the enclosure either being bad, or simply not being powerful enough. Note I used to be the upstream kernel maintainer for the Linux UAS driver for a number of years. @kaihengfeng, this issue should probably be closed as not a bug or some such. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1789589 Title: USB-SATA resets when UAS is used To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1789589/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
