Smart power strips - why?

[EightBySix]

Just about to buy one and was considering the numbers of outlets I would need etc. Then I got to thinking, why do I need one at all? What does one give me that a master power switch doesn't? Do front ends have a software shut down feature? is it about a controlled PC shutdown - not sure they are really  needed nowadays.

why do you guys use them?

[Nephasth]

That's exactly why I use one. When the computer is shut down by exiting a front end, the smart strip cuts power to all the other sockets turning everything else off, no buttons to push once you exit the front end. And since turning on the computer powers up the rest of the sockets, a simple momentary switch (such as an arcade button) is all that is needed to turn everything on with one push.

[Grimoz]

That's exactly why I use one. When the computer is shut down by exiting a front end, the smart strip cuts power to all the other sockets turning everything else off, no buttons to push once you exit the front end. And since turning on the computer powers up the rest of the sockets, a simple momentary switch (such as an arcade button) is all that is needed to turn everything on with one push.

Couldnt have said that better myself, exactly what I do on my cab.

[bullrees]

I just got one yesterday and have not used it yet. The reason I wanted one is so I can have one switch to turn on/off the master device (tv, computer, marquee lights, or sound system) and the smart strip turns on/off the rest. I haven't figured out what the best master device is with my setup yet. The basic answer is to have one button to power on/off all your mame arcade devices.

[TheShanMan]

I have my system to sleep when the power button is pressed, and a smart strip is perfect for that as well. The computer gets enough juice to maintain the sleep state yet not enough to cause everything else to turn on.

[EightBySix]

I get that a software power down via the front end might be attractive, but apart from that, what's the difference between a connection to a power switch to the pc which then powers everything else down via a smart strip, and just killing the main power....

[bullrees]

I get that a software power down via the front end might be attractive, but apart from that, what's the difference between a connection to a power switch to the pc which then powers everything else down via a smart strip, and just killing the main power....

There is the myth that if you don't shut down your computer properly via software it will cause problems but I don't think that's the case here. I'm speculating but if people want to boot right into the front end and it be seamless from power on you have to shut down windows correctly to prevent getting the "start windows in safe mode" or check disk stuff. Just a guess though.

[MonMotha]

It's not really a myth. Data loss due to improper shut down is possible.  Modern journaled filesystems (Windows NTFS, Linux ext3/4, OS X HFS+, etc.) are pretty good about not blowing up the whole filesystem, but you could still lose any newly written data (and possibly the old version, as well, for overwrites).  A proper shutdown ensures this will never happen.  Note that older filesystems like FAT, ext2, etc. found on Win98 and ancient versions of Linux (before about 2000) are not journaled and can totally blow up if you hard power the system.  I've experienced this, and it sucks; you basically get to start over from scratch.

There are ways around this.  If you can ensure that the data on the drive never actually needs to change (i.e. it should start up in the same state every time), you can use a copy-on-write (COW) ramdisk arrangement.  Windows supports this using something called the "enhanced write filter" (EWF) that's included with the XP embedded toolkit and can be installed on a standard copy of XP Pro or Win7.  On Linux, this can be done using unionfs and a tmpfs.  I don't know how to do it on OSX, but it's probably possible.  If you have a small amount of non-critical data that needs to be persistant across reboots like a high score table, you can just locate those on another partition that doesn't have this on it.  Then worst case, if the whole thing goes poof, you lose your high scores.

DOS is a bit of an odd beast in this.  DOS doesn't do any caching at all, so you can hard power it as long as it's not actively doing anything.  You just have to make sure it's not actively writing to the disk (which can be a bit hard unless you fully exit back to the command prompt), otherwise the above "you might lose everything" precautions apply.  I can't really say I would recommend anybody build a new system using DOS unless they have a very, very good reason to, though.

Now, I've hard powered modern Windows and Linux systems for years with few issues.  As long as there's not a bunch of write activity, and a typical MAME system wouldn't have much, you're usually just fine.  However, there's always the possibility of Murphy rearing his ugly head.

Most commercial PC embedded products like arcade games, cash registers, etc. use the above-mentioned COW system like EWF to make sure that they're reliable in the presence of the inevitable hard power off situations that people expect from an "appliance" type system.  Many embedded Linux systems just run the whole thing out of a ramdisk that's loaded at startup or run the entire root filesystem readonly, but neither is an option on Windows (though you can approximate the former with Windows PE).

Of course, you can also just ensure that you "properly" shut down the PC system.  That will ensure you have no problems, but it can be inconvenient.

[IronBuddha]

I use one for the exact reasons Nephasth mentioned. But I also bought one for my entertainment system for the main reasons why it was invented, which is to save some energy and money while my TV is shut off.

[wizkid32]

Personally, I plan on just using a regular power strip and leaving the speakers, USB hub, et al on.

[HanoiBoi]

I've got a smart strip and I have my pc set to 'shut down' (like a software shut down) when pressing the power button. 

Sure, I'll see and hear the Windows shutdown screen and sounds, but its a bit safer to me.

Also, I've never concerned myself with the look of the boot up or shut down.  I usually have it up before guests arrive and I shut down after they leave.   And, its not like they don't know there's a PC in there.

[TopJimmyCooks]

I've got a smart strip and I have my pc set to 'shut down' (like a software shut down) when pressing the power button. 

Bingo.  With the smart strip I can hit my power button (wired to the PC's momentary power switch) and through Windows and Mala the pc will hibernate.  Mala has good hibernate functionality and I'm sure other FE's do too.  shuts everything off, then upon a second press, quickly resumes with Mala running.  If I need to get to windows I use the mouse to exit mala.  As Monmotha pointed out, there are good reasons not to shut Windows down without closing it or sleep/hibernate. 

[Cynicaster]

I've got a smart strip and I have my pc set to 'shut down' (like a software shut down) when pressing the power button. 

I was a bit surprised to have to read so many responses before seeing this one; I didn't think anybody did it any other way.

I have everything in my cabinet plugged into a smart strip, with the PC in the master.  I walk up to my cabinet, one press of the power button turns everything on and it boots right to MaLa.  When I'm done playing, I simply make sure that I exit back into the front end to store any high scores that I might have acquired during the session (I run MamePlus, BTW), and hit the power button again, which causes the PC to do a controlled shut-down.

My smart strip was about $30, taxes in.  Of all the places to cheap out on a project, I'd say cutting out a smart strip is a poor choice.   

Sure, I'll see and hear the Windows shutdown screen and sounds, but its a bit safer to me.

Also, I've never concerned myself with the look of the boot up or shut down.  I usually have it up before guests arrive and I shut down after they leave.   And, its not like they don't know there's a PC in there.

Ditto. 

It's not real arcade hardware and I have no inclination to pretend it is.  It's a MAME machine and MAME machines use PC's for guts.  I could not care less if this fact is made apparent for a few brief moments during start up and shut down. 

 

[bkenobi]

I use one for the exact reasons Nephasth mentioned. But I also bought one for my entertainment system for the main reasons why it was invented, which is to save some energy and money while my TV is shut off.

Propaganda...  You are spending ~$30 to save you money on your electric bill.  Most of the drains that people try to scare you about are miniscule.  If you were to check what these drains actually are, you'd find that they won't cost you much.

I went around the house with a Kill-A-Watt and found that these money pits total $/year.  If you are concerned about the money, you will see that it will take years to pay for the strip.  If you are worried about the offsets, consider how much energy and chemicals go into creating the power strip.

But, if it makes you feel better about yourself, go for it.   

[Green Giant]

I always assumed this main reason was for the monitor mostly.

Most of my stuff comes up when I send power to the computer via the button, however I have a separate button to fire up my tv.

Controlling my tv power was probably the hardest part since I didn't want to hack up the tv itself.  Solution:  hack up a cheap universal remote for the power button to connect to an extra button I had laying around.




If you have a monitor that powers up upon receiving power, then a smart strip is really nice.  Otherwise it isn't so necessary.

[Gray_Area]

Propaganda...  You are spending ~$30 to save you money on your electric bill.  Most of the drains that people try to scare you about are miniscule.  If you were to check what these drains actually are, you'd find that they won't cost you much.

If you think outside of your home, the amount is quite a bit. Everyone pays for that.

If you have a monitor that powers up upon receiving power, then a smart strip is really nice.  Otherwise it isn't so necessary.

Some monitors will stay off until they receive a video signal.

I've got a smart strip and I have my pc set to 'shut down' (like a software shut down) when pressing the power button.  

I was a bit surprised to have to read so many responses before seeing this one; I didn't think anybody did it any other way.

I've thought of this, but prefer to have my front end handle shut down.


@Monmotha: what about the 'reset' button on the PC case? I notice that Windows boots back just fine (no 'Windows wasn't shut down properly' message) if I press that.

[MonMotha]

Whacking the reset button is the same as a hard power off and immediately turning it back on.  Windows has given up on yelling at users that they didn't shut down properly.  It only does that now if you interrupt the start-UP process or there's a known inconsistency indicated by the journal (which would appear random to the user); it then assumes that there may have been a problem that caused it to lock up or similar on startup (somewhat common due to updates, buggy drivers, etc.) and offers to run in safe mode for you.  On hard power off, it just recovers the journal and moves about its merry business hoping that you won't notice any problems.

The chance of data loss is in this case "relatively low", but definitely non-zero.  If you're using Windows 2000 or newer, you should never lose the entire filesystem (excepting an OS bug), but spotty data loss is possible, and if that loss is in a system file (unlikely, but possible), you could wind up with an unbootable system.  Like I said, I've done it for years with few issues, but I'd never ship a production system where users would be likely to routinely cut power without running the shutdown sequence, like an arcade game, without putting some sort of protections in place like a COW ramdisk or scratch disk.

On Win9x and DOS, total filesystem loss (as in everything goes poof and the filesystem is unusable) is entirely possible.  Be careful if you're still running one of these ancient OSes.

[Gatt]

Whacking the reset button is the same as a hard power off and immediately turning it back on.  Windows has given up on yelling at users that they didn't shut down properly.  It only does that now if you interrupt the start-UP process or there's a known inconsistency indicated by the journal (which would appear random to the user); it then assumes that there may have been a problem that caused it to lock up or similar on startup (somewhat common due to updates, buggy drivers, etc.) and offers to run in safe mode for you.  On hard power off, it just recovers the journal and moves about its merry business hoping that you won't notice any problems.

The chance of data loss is in this case "relatively low", but definitely non-zero.  If you're using Windows 2000 or newer, you should never lose the entire filesystem (excepting an OS bug), but spotty data loss is possible, and if that loss is in a system file (unlikely, but possible), you could wind up with an unbootable system.  Like I said, I've done it for years with few issues, but I'd never ship a production system where users would be likely to routinely cut power without running the shutdown sequence, like an arcade game, without putting some sort of protections in place like a COW ramdisk or scratch disk.

On Win9x and DOS, total filesystem loss (as in everything goes poof and the filesystem is unusable) is entirely possible.  Be careful if you're still running one of these ancient OSes.

I would disagree that it's relatively low.  IIRC,  newer Windows versions do defrag in the background periodically without user intervention,  and a hard reboot at the wrong time would cause some pretty serious problems there.  I could see a situation where it's doing defrag where it could easily hose the drive.  Especially with delayed write caches in either Windows,  or the HD's buffer,  since modern drives pack 16 or 32 megs of buffer at least.

I would also argue that you could potentially hose Windows with ease,  since it's never shutting down processes and services properly.

I realize that it's alot less risky than it once was,  but I would argue that it's a significant risk,  even if a limited one in scope.  Plus,  it wasn't all that long ago I hosed a drive by doing hard reboots while trying to excise one of those fake virus scanner demons.  Something must've been updating the MFT at precisely the wrong time,  because I lost the MFT, and consequently the drive.

[MonMotha]

The caching issues (both the OS write cache as well as the cache on the hard drive) are solved by inserting "barriers" within the cache schedule.  Re-ordering writes around these barriers is not permitted.  I know Linux does this with ext3 and ext4.  Windows should at this point; it's not a new technique.  Hardware support is a bit more spotty, but it can be emulated (at a performance cost) if the hardware doesn't support it.  Linux actually maintains a blacklist of drives that claim to support cache barriers but actually ignore them.

If the OS actually journals the filesystem and uses write barriers (and the drive actually implements them or the OS otherwise knows that it doesn't) correctly, it should not be possible to hose the entire filesystem.  You could lose data (unless that's journaled, too, but that's uncommon due to the severe performance hit) in the form of truncated files or missing files, but the filesystem metadata should always be in a "consistent" state meaning you shouldn't lose everything.

Now, that's a pretty high assumption as it's tough to get right, but it's at least guaranteed by the design of a journaled filesystem.  I'd like to think they've worked most of the bugs out of NTFS at this point given that it's well over a decade old...

I don't know if the Windows defrag program honors any of these guarantees.  It damn well should since it would be a glaring hole in an otherwise reasonably well designed system to ignore them, but it can't really be inspected.

Also, as you note, if data loss or corruption occurs in a critical system file, the OS could be rendered unusable.  It's considered good practice to make the OS as tolerant of this as possible, and Windows is surprisingly good at it.

My suggestion of "the risk is low" is experience driven, though.  I've killed the power to both Windows XP and Linux ext3 systems without shutting them down for basically as long as they've been available, both intentionally and unintentionally, and I don't think I've ever lost an entire filesystem.  In one case, this happened daily for over a year (a one-off test arcade system).  I don't think I've ever even ended up with an unbootable OS.

I *have* lost entire FAT and ext2 (both are not journaled) filesystems, despite my not having done nearly as much with them.  I *have* also lost data, even on NTFS and ext3/4, due to hard power down, and that's definitely bad, hence my suggestion that you should always shut down properly or use another means of ensuring things don't break like COW to a ramdisk or scratch drive, but I've never lost an entire filesystem.  The design criteria of a journaled filesystem are supposed to guarantee this exact behavior, so I'd tend to believe the implementors have gotten it at least mostly right.

All the commercial PC arcades I've torn down use some form of ramdisk to contain writes and discard them on reboot, always bringing the system up in the "factory" state (high scores and operator settings are stored elsewhere with checking to see that it's OK and blowing them away with the defaults if they're not).  On Windows, this is called EWF: the Enhanced Write Filter.  

Unfortunately for a typical MAME builder, these aren't the easiest things in the world to set up.  EWF doesn't ship with XP Pro (it comes with the XP embedded toolkit), though it can be installed by hand, and the only way to manage it is a somewhat obscure command line tool.  Doing a UnionFS/tmpfs on Linux is also rather complicated (probably more so, but also more flexible); there are other options on Linux that are easier and more typically deployed (system in initrd + data on readonly partition is the most common).

I guess what I'm saying is that it comes down to whether or not you feel lucky, punk.  I'd wager that most users will never have a problem, especially given the largely static nature of a typical MAME setup, but like I said, I'd never ship a production system like this without addressing this problem.

[BobA]

Let's just say that a smart strip is CHEAP insurance.  I'd rather do it right than have to rebuild a drive even if it only means formatting it and copying the HD.    

I don't think it saves that much electricity in the long run but is sure saves on all the other components in the cab by letting them power down so they do not burn out as quickly.  Most monitors go into a low power state without signal and the amp is not being driven to it's power usage is also low but that flourescent light in the marquee if you are not using leds uses real power.

[wizkid32]

Honestly, how much power do you think those speakers are going to take that a smart strip will, "save you hundreds!"