Hi Damien -- > > This tells us that the maximum size the device can support is 256KB > > (max_hw_sectors_kb) > > and the maximum size that the kernel allows is 256KB (max_sectors_kb). > > Which highly depends on the HBA since the hard-disk interface will accept much > larger commands. This 256KB on your system seems to be very low. What HBA are > you using ? These days, most SAS HBAs have at least 128 or 256 segments, which > allow up to 512KB/1MB IOs. SATA/AHCI is limited at 169 segments for up to 32MB > max_hw_sectors_kb (and 1280 KB max_sectors_kb). > > > Additionally, the DMA engine is limited to 2048 segments of IO, > > each with a max size of 64KB. > > That's a lot. I wonder why max_hw_sectors_kb end up so small. I'm trying a Raspberry Pi for this testing so only have a USB3 interface available. Seems to be fast enough but maybe that's why it's giving numbers that seem odd to you? > The list of WD drives using SMR as drive-managed is published. See: > > https://blog.westerndigital.com/wd-red-nas-drives/ > > and > > https://blog.westerndigital.com/wp-content/uploads/2020/07/WD_SMR_SKUs_vDS.pdf > > Your drive is not on the list :) I wasn't sure that the list was reliable when it came to white label drives, but it's good to have it confirmed. Many thanks! Ian ...
