13.07.2019 12:22, R. Schwartz пишет: > My HDD (one partition, BTRFS) reports itself as non-rational: > > $ cat /sys/class/block/sda/queue/rotational > 0 > > According to btrfs(5), by default, BTRFS detects this value and turns on > SSD optimizations for the HDD. Naturally, I'm puzzled... > > My question is: should I use the nossd mount option for the HDD? > > Following is more details about this HDD. > > It's a recent Western Digital Blue 2TB HDD, model WD20EZAZ. Given its > cache size is a rather large 256MB, some people say it's likely an SMR > (shingled magnetic record) HDD. > > Since Host-Managed and Host-Aware SMR HDDs support the `REPORT_ZONES` > ATA/SCSI command, I ran this test using `sg3_utils`: > > # sg_rep_zones -R /dev/sda > Report zones command not supported > sg_rep_zones failed: Illegal request, Invalid opcode > > Therefore, _if_ it's SMR, it must be Drive-Managed SMR. > > So is there a good reason why the HDD reports itself as non-rotational? kernel sets non-rotational flag according to Medium Rotation Rate field in Block Device Characteristics VPD page (0xb1). What sg_vpd -p bdc /dev/xxx says? > Does it have to do with SMR? > > Additioanlly, the HDD is connected through a SATA to USB connector. I > original suspected it was an issue with the connector, but I tested with > other HDDs with the same connector and they all report as rotational. >
