Re: Is there a way to stop a SATA disc?
On Mon, Jul 13, 2009 at 07:35:27PM +0100, Barry Samuels wrote:
> If I issue the command 'sg_start --stop /dev/sdb' I hear a click from the
> computer as if the drive is being switched off but can't detect any
> difference in noise. That could be because the drive is ultra quiet but if
> I then try to mount a partition on the drive it mounts instantly. With the
> previous drives if I did that there would be a significant pause whilst
> the drive was spinning up to running speed.
>
> Does the fact that there is no pause of any sort when mounting the drive
> mean that it hasn't stopped?
No --- the drive could be fast and have a cache and/or be designed to
come back without delay because it turns itself off eventually.
It's not a SCSI device anyway and may not understand/support the SCSI
commands you're trying to use. SATA performs somewhat better than IDE,
but it is totally unreliable --- and lightyears away from SCSI in
every aspect.
Doesn't it work when you use hdparm to set a spin-down time for the
disk? With hdparm, you can also query the current status of the disk
--- that's probably the best way to find out if the disk is sleeping
or not, short of measuring how much power it draws.
But then, why don't you use the new disks for a RAID-1 and the old
disks for backups? I have seen too many disks, including new ones, go
bad to put data onto a single disk, and the non-existent reliability
of SATA alone has made using at least a RAID-1 a requirement.
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