You are not logged in.

#1 2018-03-07 11:06:17

taric
Member
Registered: 2018-01-10
Posts: 31

iMac 27` fusion drive

I have installed arch on newly bought iMac 27` which has a 2TB fusion drive.
When I'm booting into OSX but not using the iMac, it stops using and spinning the hard disks, then when I wake it up, I can hear the drive waking up.
On Arch however, no matter what i'm doing, the hard drives are always spinning.

Is there a way to stop doing that? And if not, is that bad for the hard drive on the long term?

Offline

#2 2018-03-07 11:19:45

Pryka
Member
Registered: 2018-02-07
Posts: 69

Re: iMac 27` fusion drive

You could probably control spin-down time with hdparm

I'm using it to stop my desktop HDD from head parking.

From my experience is better to let the HDD spin all the time rather than start and stop every 30 seconds. But thats only on Desktop, head parking and spinning down can be quite useful on laptops.

Last edited by Pryka (2018-03-07 11:20:24)

Offline

#3 2018-03-07 11:53:28

taric
Member
Registered: 2018-01-10
Posts: 31

Re: iMac 27` fusion drive

❯ sudo hdparm -B /dev/sda

/dev/sda:
 APM_level	= 192

If my understanding is correct, because the value is greater than 127, then the disk will never spindown. Accordingly, I need to set it to at most 127 like thus:

❯ sudo hdparm -B 127 /dev/sda

/dev/sda:
 setting Advanced Power Management level to 0x7f (127)
 APM_level	= 127

Right?

Offline

#4 2018-03-07 11:59:18

Pryka
Member
Registered: 2018-02-07
Posts: 69

Re: iMac 27` fusion drive

Yes.

Also add the udev rule to the system. Because these settings will restart to default value after reboot.

Here you can see how to do it - https://wiki.archlinux.org/index.php/hd … _udev_rule

Offline

#5 2018-03-07 13:29:26

taric
Member
Registered: 2018-01-10
Posts: 31

Re: iMac 27` fusion drive

I used the smallest setting:

/dev/sda:
 setting Advanced Power Management level to 0x01 (1)
 APM_level	= 1

And that still did not make the HDD spin down.

Side question: is there anything bad that could happen if an HDD was to spin all the time?

Offline

#6 2018-03-07 16:46:04

Pryka
Member
Registered: 2018-02-07
Posts: 69

Re: iMac 27` fusion drive

In a laptop there is a risk that you may hit or shake computer with some semi heavy force and that is where the head parking and spin-down come in handy. When the head normally works it floats above the HDD plates. When you hit/drop or whatever, there is a chance that head will make a physical contact with the plate and damage it. Head parking ensures that head is not used when is not needed so it can't make contact with plate accidentally. So it's basically just minimize the probability. There is always chance that you will drop laptop while read/write data. big_smile

Spin-down it's almost always just a battery life saving feature.

But remember certain drives have fixed numbers where the probability of failure due to constant work rise. Some Seagate HDD's have solid numbers of Load_Cycle_Count after you pass that they don't respect warranty. smile On the other hand no spin-down more power on hours. There is no golden solution and any middle ground option for this.


On my Desktop I always turn OFF spin-down and head parking. It's basically useless in stationary computer.

Last edited by Pryka (2018-03-07 16:56:04)

Offline

#7 2018-03-08 05:23:07

taric
Member
Registered: 2018-01-10
Posts: 31

Re: iMac 27` fusion drive

Well, I'm on an iMac which is pretty much a stationary computer, so I guess neither spin-down nor head parking matter.
But, I was curious how I could emulate what OSX does when it basically shuts the disk down when it is not used while arch kept on spinning it.

So I guess there is no easy way to make that for arch right?

Thx for the help!

Offline

#8 2018-03-08 07:47:28

Pryka
Member
Registered: 2018-02-07
Posts: 69

Re: iMac 27` fusion drive

No idea. hdparm was/is always working for me, for now. So i really don't know. Maybe there is some other tool around?

Offline

#9 2018-03-08 11:24:39

Ropid
Member
Registered: 2015-03-09
Posts: 448

Re: iMac 27` fusion drive

There's another parameter "-S" for hdparm. In the man-page, it says this:

Put the drive into idle (low-power) mode, and also set the standby (spindown) timeout for the drive.  This timeout value is used by the drive to determine  how  long to wait (with no disk activity) before turning off the spindle motor to save power. Under such circumstances, the drive may take as long as 30 seconds to respond to  a subsequent  disk  access, though most drives are much quicker.  The encoding of the timeout value is somewhat peculiar.  A value of zero means "timeouts are disabled": the device will not automatically enter standby mode.  Values from 1 to 240 specify multiples of 5 seconds, yielding timeouts from 5 seconds  to  20  minutes.   Values from 241 to 251 specify from 1 to 11 units of 30 minutes, yielding timeouts from 30 minutes to 5.5 hours.  A value of 252 signifies a timeout of 21 minutes. A value of 253  sets a vendor-defined timeout period between 8 and 12 hours, and the value 254 is reserved.  255 is interpreted as 21 minutes plus 15  seconds.   Note  that  some older drives may have very different interpretations of these values.

Last edited by Ropid (2018-03-08 11:26:56)

Offline

#10 2018-03-08 11:37:07

Pryka
Member
Registered: 2018-02-07
Posts: 69

Re: iMac 27` fusion drive

^^^

This! Thank You Ropid I confused -B with the -S... -B is for head parking.

Anyway -B must be 127 or bellow to turn on/activate spin-down option witch is set by the -S.

Sorry for the commotion...

Last edited by Pryka (2018-03-08 11:46:25)

Offline

Board footer

Powered by FluxBB