On Tue, Sep 11, 2012 at 06:03:44AM -0700, Rich Shepard wrote: > Gotcha'. Will do. I cannot believe the WD drives are failing when the > common factor is the enclosure.
Sadly, there are many poorly designed bridge chipsets in external enclosures. Linux adheres to standards, and goes fast. Windows is slower, and often has tweaks or vendor-supplied drivers that are nonstandard, but patch over flaws in the chipsets. I had similar problems with some brands of USB2-to-IDE enclosures, years ago. See http://wiki.dirvish.org/USB2Drives I can only speculate why, but perhaps the interface chip designer did not put in enough buffering between the clock domain of the drive and the clock domain of the USB interface. A small fraction of the data transfers will line up wrong, and some of the bits of a byte will transfer on clock cycle N and some on clock cycle N+1. There are known ways to add buffering to reduce this problem to infinitesimal error rates, but many inept digital designers don't know about them, or how to do the analysis and the testing. Rsync-based dirvish keeps hard drives very busy. So does an external "write a lot / read a lot " program, which might be a good way to test out the enclosures and their interface chips without risking your backups. Different kernels may have different error recovery behavior; some smart USB driver programmer might add a retry patch for one version of the kernel, and a subsequent clueless programmer might improve average performance by a fraction of a percent in a subsequent driver by taking the patch back out again. Sadly, there is a lot of "cruelty free" (untested) design out there. So, find out what chipset the enclosure uses with "lsusb", and try an enclosure with a different chipset, and report your findings here and on the dirvish wiki. Sometimes, the only way to deal with this stuff is to carefully document our problems on the web so our Linux brethren can avoid them. Keith -- Keith Lofstrom [email protected] Voice (503)-520-1993 KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon" Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
