Does my Mac support Safe Sleep?

Question

Level 1

9 points

Does my Mac support Safe Sleep?

Hello,

I switched to Mac some time ago (after I became more and more uncomfortable with Windows), but carried over some good old rituals too.

For example, I switched off my Mac everytime I left it, as my first experience with Windows sleep mode was: the Computer beeps and blinks, but isn't faster in wakeup than booting. Now, I first put my iMac in sleep mode and I was amazed and shocked by the 3-second-wakeup, I was able to use the computer as soon as the monitor went on! It was almost instant. So, I did some research on the internet if it was possible (or recommendable) to put iMac in sleep mode rather than switching it off for a longer period of time, for example several hours (resulting in a total uptime of several days when repeatedly doing this). I found out pretty soon that there are three sleep modes, "sleep" (hibernatemode 0), "hibernate" (hibernatemode 1) and "safe sleep" (hibernatemode 3). By using

pmset -g | grep hibernatemode

I found out that my iMac is in hibernatemode 0, so it leaves the RAM powered while everything else is shut down. I am a little worried, because in case of a power failure some data might get corrupted (although I quit all apps before putting it to sleep). I live in a region where power outages happen once a year maybe, so it would not be unstable enough to buy an UPC, but it is not safe enough to just trust the supply. I would be very satisfied if I could put my iMac into hibernatemode 3, where both happens, the RAM stays powered (so it wakes up instantly) but it also generates a sleep image that the iMac can recover from if there is a power outage.

Now, I am wondering if my iMac supports hibernatemode 3. I know how to put it in safe sleep mode, but I am afraid of it not being supported.

My system: iMac late 2007 (20" model) with 2GHz Intel Core2Duo, ATI Radeon HD2400XT and 2GB RAM, running OS X 10.8.3. Current hibernatemode is 0.

Posted on Mar 30, 2013 1:45 PM

Reply

Answer 1

Mar 30, 2013 2:22 PM in response to Mr. iPadfan

Let me try to cut to the chase. I have a late 2009 iMac. I live in a semi-rural area where there can be power outages during bad weather conditions. I do not have a UPS.

The instruction book that came with my iMac says to put it to sleep unless you're not going to use it for more than a few days, in which case you turn it off. I have my "Energy Saver" set to put the computer and display to sleep after 3 minutes of non-use and that's what I normally use. I also have it set in the "Energy Saver" so that it will NOT turn on automatically if the power is restored. If I know (or even suspect) that there's going to be the kind of weather that'll cause a power outage, I turn my computer and my printer off. I'll turn things on once power has been restored and I'm reasonably certain that the weather has improved.

The routine works for me OK.

Reply

Answer 2

Mr. iPadfan Author

Level 1

9 points

Mar 30, 2013 2:33 PM in response to Chessie 01

➖ I am sorry, but this does not resolve my problem. 😐

As I said, once or twice a year there is a power outage, but it is not predictable because it is not related to weather condition. I am looking for a solution where I do not need to care if there is a power outage while I sleep deeper than my Mac.

ℹ Basically it's just this simple question to anyone who knows: does my iMac model (late 2007 (20" model) with 2GHz Intel Core2Duo, ATI Radeon HD2400XT and 2GB RAM, running OS X 10.8.3) support Hibernatemode 3 alias "Safe Sleep" to protect my Mac against damages due to power outage?

Reply

Answer 3

Linc Davis

Level 10

209,547 points

Mar 30, 2013 6:21 PM in response to Mr. iPadfan

You can set hibernatemode 3, but it will do nothing to protect the machine from damage by a power surge or outage. All it will do is to protect unsaved data in memory. If you quit all applications before sleeping, that's not an issue.

Reply

Answer 4

John Galt

Level 10

141,060 points

Mar 30, 2013 7:32 PM in response to Mr. iPadfan

Mr. iPadfan wrote:

... does my iMac model... support Hibernatemode 3 alias "Safe Sleep" to protect my Mac against damages due to power outage?

You can set hibernate mode to 3, but it seems to me its only benefit could be if power were to be lost after the iMac was already sleeping. Sleepimage is written to disk prior to system sleep. If your iMac lost power while it was "awake" you would certainly lose any unsaved work no matter what hibernate mode you choose.

The problem is that an iMac without power no longer sleeps, it's dead. Upon restoring power you need to cold boot, and I seriously doubt sleepimage can be forced to load in that event. Sleepimage is loaded upon wake from "safe sleep", not from boot as far as I know.

It is simple enough for you to try, so go ahead and see if it does what you want. Other than creating a 16 GB sleepimage file it did not appear to do anything beneficial on the iMac I am using though (a later model).

The file location is /private/var/vm/sleepimage

Configure hibernatemode, verify the file is created, do some work on your Mac, don't save it to disk (and don't use Pages or similar app that saves work on its own), let it sleep, then pull the plug. I think you will see what I mean.

Reply

Answer 5

John Galt

Level 10

141,060 points

Mar 30, 2013 7:46 PM in response to Mr. iPadfan

... I live in a region where power outages happen once a year maybe, so it would not be unstable enough to buy an UPC, but it is not safe enough to just trust the supply.

There are other benefits to using a UPS. After coping with numerous power problems (more like once a day) I finally bought several of them. The iMac's power supply must be fairly robust since none of them ever failed, but I have seen other equipment damaged by power anomalies.

Any UPS with a USB communication feature can be used to automatically shut down your Mac in an orderly fashion, while unattended, in the event of a power failure. No additional software is required. Plug it in and it works. Small capacity models are available for around $50.

Reply