From: "R. Schwartz" <email@example.com> To: "firstname.lastname@example.org" <email@example.com> Subject: Should nossd mount option be used for an HDD detected as non-rotational? Date: Sat, 13 Jul 2019 09:22:20 +0000 Message-ID: <htetrjLP1jLMK9WTasfT2e5ZdkY1yV0iY3PHjVEDqCKIZ8d2VwdRTBRezsUAxzKawi_lsxBi5HYfOlvyByGPBwswTCKXSt_lbhRCAmQZ2Qgfirstname.lastname@example.org> (raw) 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? 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.
next reply index Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-07-13 9:22 R. Schwartz [this message] 2019-07-13 11:06 ` Andrei Borzenkov 2019-07-13 11:18 ` R. Schwartz
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