Mikulas, > Do you think that SSDs benefit from more alignment than 4K? It really depends on the SSD. > If you have some SSD that has higher IOPS with alignment larger than > 4K, let me know. Absolutely. There are devices out there reporting characteristics that are not intuitively correct. I.e. not obvious powers of two due to internal striping or allocation units. Some devices prefer an alignment of 768KB, for instance. Also, wide RAID stripes can end up causing peculiar alignment to be reported. Instead of assuming that 4KB is the correct value for all devices, I'd rather address the cases where one particular device is reporting something wrong. I'm willing to entertain having a quirk to ignore reported values of 0xffff (have also seen 0xfffe) for USB-ATA bridge devices. But I don't think we should blindly distrust what devices using other transport classes happen to report, it's usually only USB bridges that are spewing nonsense. Which is why we typically avoid trying to make sense of VPD pages on USB in the first place. -- Martin K. Petersen Oracle Linux Engineering
