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Parity check/sync "auto-throttling" feature

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Tom M's idea.  Not sure when this will be added, but we want this to happen...

 

At present parity check/sync operates as fast as possible because ppl like to use it as a benchmark of their setup.  But in actual practice, when you try to do normal work when there's a parity check/sync in the background, it greatly impacts normal I/O transfer rate.  I can should add code that gives normal I/O priority over parity sync/check.
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Good idea.  Many disk-intensive utilities do this in the "Windows world" => virus scans; antimalware utilities; automated cloud backup utilities (e.g. Carbonite);  etc.    If they detect other activity, they either suspend or at least slow down their own use of the system resources so the system's responsiveness isn't impacted.

 

This has been discussed in the past, and a few folks objected because they "... always want parity checks and disk rebuilds to work at maximum speed ..."  ==> that's simple to do ... just don't use the system for other purposes during one of those operations, and suspend any add-ons that would be doing so.

 

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I for one would love to see this implemented.  Those with lower powered servers (especially those with lower CPU power) could benefit considerably in terms of the general usability of the server during parity checks.  And just rescheduling the check is not always an option.

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Combine this with incremental parity checking/resuming and you have a great way to make parity checking a completely transparent event, when desired.  It could be scheduled and or triggered in the background for any number of reasons without the user's intervention.  And with good resuming, it can be assured to complete, even if the server is rebooted.

 

Also keep the current manual option so people can feel good about it.  ;)

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+1 for this feature, I would love if scan throttling also responded to disks temp as well, my drives are running way too hot for comfort during scans on warmish days and I don't have room in the case for more fans (currently 3x120mm running 100% all the time), I'm at a point where I'm considering cutting into the side and front panels to add fans...

My thinking is that the scan would pause when a disk goes above warning temp and resume when it's below minus a few degrees or a set value maybe.

If the scan could pause for the mover it would avoid endless thrashing also.

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+100

i know I should do parity checks more often than I do (manually) and just have them scheduled but hate taking the WAF hit when it causes impact. In the meantime, is there a method to throttle it manually with some setting?

 

especilly with drives getting bigger and bigger, therefore checks taking longer and greater chance of impact

Edited by graywolf

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@graywolf yup, 6TB drives take 14-16 hours to scan on my system, starting at 36°C,  6 hours in the scan I'm nearing 60°C on all 8 drives and if the mover is active all bets are off in terms of duration...

 

In the meantime I ordered 3 industrial PPC fans, they do magic in my other rigs, I hope they'll improve cooling overall but I don't think they'll change anything for parity scans, it's too much heat too fast. :/

Edited by kyis

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13 minutes ago, kyis said:

6 hours in the scan I'm nearing 60°C on all 8 drives

 

You clearly need better cooling, none of my disks goes above 40C during parity checks, and 60C is the max for most disks, and you don't want to be nowhere near that, <45C is considered safe.

Edited by johnnie.black

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@johnnie.black Yup that's why I'm fretting, I don't want to wait for winter to do parity checks. ^^

I've got a DS380 case with 8 drives, that's a lot of drives in a tiny space and not a lot of cooling solutions. The new fans I ordered should ideally triple the airflow but even then I'm not sure it'll be enough. I have no way to control ambient temp, goes from 16°C in winter to 26°C in summer. If the new fans don't cut it, I'll be looking if I can contribute some code to do what I need and if it's beyond me I'll be cutting into the case to pull air through the HDD cage. B|

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29 minutes ago, kyis said:

@johnnie.black Yup that's why I'm fretting, I don't want to wait for winter to do parity checks. ^^

I've got a DS380 case with 8 drives, that's a lot of drives in a tiny space and not a lot of cooling solutions. The new fans I ordered should ideally triple the airflow but even then I'm not sure it'll be enough. I have no way to control ambient temp, goes from 16°C in winter to 26°C in summer. If the new fans don't cut it, I'll be looking if I can contribute some code to do what I need and if it's beyond me I'll be cutting into the case to pull air through the HDD cage. B|

 

See here for some mods to improve cooling in the DS380:

 

 

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@johnnie.black thanks, I know what I'm doing after work tomorrow. xD

It'll be hell to reroute all the cables cleanly but I'll give the skirt a try, my idea was a bit more destructive, cutting 120mm holes in the side panel and putting 2 fans to pull air out so airflow would be forced through the HDD cage.

 

Edit:

Adding the skirt didn't change much, I assume the fans didn't have enough static pressure to begin with. Installing the PPC fans made a huge difference, they keep everything at 11°C above ambient when running at 30% with a huge margin if things start to heat up.

Edited by kyis

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On 25/05/2017 at 6:57 PM, kyis said:

+1 for this feature, I would love if scan throttling also responded to disks temp as well, my drives are running way too hot for comfort during scans on warmish days and I don't have room in the case for more fans (currently 3x120mm running 100% all the time), I'm at a point where I'm considering cutting into the side and front panels to add fans...

My thinking is that the scan would pause when a disk goes above warning temp and resume when it's below minus a few degrees or a set value maybe.

If the scan could pause for the mover it would avoid endless thrashing also.

 

Maybe you have already made sure this is ok, but double check the airflow in your system... I used to have a system that just ran to hot and it appeared that the exhaust fan was actually blowing inwards ;-)  Front fans mostly should pull air -into- the case and back fans should blow it out again..

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16 minutes ago, Helmonder said:

Front fans mostly should pull air -into- the case and back fans should blow it out again..

Unless the front fans don't actually blow on the hard drives, in which case they should blow out as well. ALL incoming air needs to pass over the hard drives first, every other opening either needs to blow out or be blocked off. All this assumes a decent number of hard drives, typical of a classic unraid server. These new fangled concoctions with only 1 or 2 drives and multiple video cards for passthrough follow all the classic rules of cooling a gaming PC.

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My rig runs cool pretty much all the time, it's only on parity check do the drives get toasty.  I do not want my server revving away making noise 29-30 days a month unnecessarily, so some sort of thermal throttling would be ideal. 

 

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On ‎6‎/‎29‎/‎2017 at 9:34 AM, HellDiverUK said:

My rig runs cool pretty much all the time, it's only on parity check do the drives get toasty.  I do not want my server revving away making noise 29-30 days a month unnecessarily, so some sort of thermal throttling would be ideal. 

 

You can get thermally controlled fan controllers that would run the fans at low speeds most of the time, but would ramp them up when the drives got warm (you just put one of the sensors for the controller on a drive).

 

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12 hours ago, garycase said:

You can get thermally controlled fan controllers that would run the fans at low speeds most of the time, but would ramp them up when the drives got warm (you just put one of the sensors for the controller on a drive).

 

 

Or....Limetech could make unRAID pause for a few minutes while the drives are too hot, using SMART temps.  Which is what this feature request is about.  It's not a feature request for an external fan controller janky-solution.

 

It's nothing unusual, StableBit Drivepool stops/pauses it's disk scanning operations while drive temps are high, and continues when they've normalised.  It'll even cycle through drives so they're all similar temps.

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1 hour ago, HellDiverUK said:

 

Or....Limetech could make unRAID pause for a few minutes while the drives are too hot, using SMART temps.  Which is what this feature request is about.  It's not a feature request for an external fan controller janky-solution.

 

Having fans ramp to required speed based on component temperature is a far more elegant solution than halting operations because of overheating. 

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1 hour ago, -Daedalus said:

 

Having fans ramp to required speed based on component temperature is a far more elegant solution than halting operations because of overheating. 

 

Agree, like with with the IPMI plugin, users with supported Asrock Rack models and Supermicro X10/X11 can already do that.

 

Edit to add: Obviously not all boards support this, but it's the best solution for boards that do.

Edited by johnnie.black

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There's the point there - very few boards support proper fan control depending on HDD temp, if any.  unRAID should be supporting the many, not the few.  

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On 7/1/2017 at 4:20 PM, HellDiverUK said:

There's the point there - very few boards support proper fan control depending on HDD temp, if any.  unRAID should be supporting the many, not the few.  

Few motherboards supports fan control based on HDD temp.

 

But lots of motherboards supports manual fan control.

 

So if the machine just had a program that looked at the SMART data and made use of the manual fan control feature of the motherboards, it would be possible to make lots of systems able to adjust the fan speed based on disk temperatures.

 

One thing to remember is that s standard HDD does not need very much air to keep reasonably cool - but there must be air movement and the air should preferably be from the room and not already hot air from the CPU. In most situations where disks runs hot, it's because hardly any air blows past the disks - the air takes other routes or there are cables or other things blocking the air. So priority 1 is to figure out exactly how the air is moving in the case.

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+1 and it doesn't need to be sophisticated. A settings box to limit parity sync / check speed to x MB/s (set to 0 for no limit) is sufficient.

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+1   I'm a member of the camp that delays doing parity checks because I don't want my server to be out of commission for a whole day.  If this feature were added I'd do Parity checks much more frequently.  

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Posted (edited)

Have you seen the new Parity Check Tuning plug-in (requires UnRaid 6.7 rc3 or later)?   It doesn’t limit the speed but does allow you to split parity schecks on a schedule when the system is likely to be less active (such as overnight)

 

Edited by remotevisitor

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This would be a very welcomed feature! Especially after a power outage. If I can schedule the parity check it's not a huge deal. But even a small blip in power makes the server slow for hours because of the parity check. 

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