-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 1/17/2014 2:31 PM, Dan Williams wrote: > Once dpm_resume of the disk is asynchronous, is there much > incremental gain by further deferring spin up? The drawback of > doing on-demand resume of the disk is that you incur the full > resume latency right when you need the data. System resume is a > strong hint to warm the disks back up, and they will go back to > sleep if unused. It isn't a strong hint to warm the disks back up at all. You *may* access *a* disk soon after resume, then again, you may not. Either way, it isn't good to spin up *all* disks after a resume only to have them stop again after a few minutes when they aren't accessed. It puts needless wear and tear on disks. > Of course it reduces the power savings if dpm_suspend/resume is a > frequent occurrence. However, are systems that make aggressive use > of system suspend shipping with rotating media, or do they ship > with disks that are cheap to resume? If suspend is not frequent I > wonder if it is worth the trouble/latency cost to keep the disk(s) > asleep. The vast majority of systems still use HDD; SSD isn't *that* popular. Also there is the power savings of leaving the disk in standby when there is no need to "spin" it up, which while fast on an SSD, does still increase power consumption and so should be avoided. In any case, this will have no affect for most people since ATA disks spin up on their own by default. In my case, I have a backup disk that I rarely access so I enabled power up in standby on the disk and don't want the kernel starting and stopping it every time I resume. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJS2ZdsAAoJEI5FoCIzSKrwsm0H/3JyAGvgRF2GWZquo7o+z9Mr dUpkKfEvWpP5ZbrM+aJ6pJ6CUNABjpq4U+kjrEQ+KdydpStSokOLWPlwxBQbTm6R oz9SAfBofZJHTPa2Jzxadh6atHSSzTg8HOQBmJ5aVU0gGOJR5wo3b8ddSAEBAXLH NftNMwqOxgvrqG3GMmN1aAJV5qAXjJe1itAfnTfvbfBjrBqI15aIDCDXom+a5zj9 wUO7tuaoB+O3S5lI4eaeY5VIQrh5AbaozJST2s4Nzch9T/Ki5LEDDCVooUaQ+aU2 lEfJZbSMttD+J/SiTLnPoIPxEe72c7JcemjE0r7aPqLeE8AZHYrylttvIHIIStA= =It+N -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
