Added Cache drive with only slight improvement in writing speed.


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Newbie here.

Setup my first unraid build about 6months ago and recently I added a cache drive but I'm not seeing much faster transfer speeds. From 3 different windows 7 machines I'm seeing ~35MB/s write speed to a cache share on a gigE switch.  Writing to a non cache share I'm getting ~30MB/s which from what I read is normal.  I thought maybe my sata II 7200rpm cache drive was too slow but it's the same drives I have in a windows box and I can get 95MB/s between them.  When I write directly to the cache drive i get more than twice the speed at 75MB/s.  Is that normal? why is writing directly to the cache drive so much faster than to a cache share?  Since I can get that speed directly to the drive it doesn't look to be a network issue but I have changed out the switch and cables but nothing has helped.  Also my read speeds are ~65MB/s which seem slower than what most people are seeing.  I thought maybe it was my MB/Cpu combo but I've read plenty of people running the same with better speeds.  Any assistance would be greatly appreciated.

 

MB: Asus C60M1-i

HD: 3TB WD red's

Cache HD: Samsung Sata II

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How do you define 'cache share'?

1. Is that a share that is ONLY on the cache drive?

2. Is that a share that is ENABLED to use the cache drive?

3. Is that something else entirely?

 

 

(maybe post a screen shot of the cache share configuration web page?)

 

number 2.  I'll post a screen shot when I get home if it'll help.

 

thanks

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Newbie here.

Setup my first unraid build about 6months ago and recently I added a cache drive but I'm not seeing much faster transfer speeds. From 3 different windows 7 machines I'm seeing ~35MB/s write speed to a cache share on a gigE switch.  Writing to a non cache share I'm getting ~30MB/s which from what I read is normal.  I thought maybe my sata II 7200rpm cache drive was too slow but it's the same drives I have in a windows box and I can get 95MB/s between them.  When I write directly to the cache drive i get more than twice the speed at 75MB/s.  Is that normal? why is writing directly to the cache drive so much faster than to a cache share?  Since I can get that speed directly to the drive it doesn't look to be a network issue but I have changed out the switch and cables but nothing has helped.  Also my read speeds are ~65MB/s which seem slower than what most people are seeing.  I thought maybe it was my MB/Cpu combo but I've read plenty of people running the same with better speeds.  Any assistance would be greatly appreciated.

 

MB: Asus C60M1-i

HD: 3TB WD red's

Cache HD: Samsung Sata II

 

Is Use Cache selected in the per share config? It is configured individually for each share.

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Newbie here.

Setup my first unraid build about 6months ago and recently I added a cache drive but I'm not seeing much faster transfer speeds. From 3 different windows 7 machines I'm seeing ~35MB/s write speed to a cache share on a gigE switch.  Writing to a non cache share I'm getting ~30MB/s which from what I read is normal.  I thought maybe my sata II 7200rpm cache drive was too slow but it's the same drives I have in a windows box and I can get 95MB/s between them.  When I write directly to the cache drive i get more than twice the speed at 75MB/s.  Is that normal? why is writing directly to the cache drive so much faster than to a cache share?  Since I can get that speed directly to the drive it doesn't look to be a network issue but I have changed out the switch and cables but nothing has helped.  Also my read speeds are ~65MB/s which seem slower than what most people are seeing.  I thought maybe it was my MB/Cpu combo but I've read plenty of people running the same with better speeds.  Any assistance would be greatly appreciated.

 

MB: Asus C60M1-i

HD: 3TB WD red's

Cache HD: Samsung Sata II

 

Is Use Cache selected in the per share config? It is configured individually for each share.

 

Yes.  Here is a screen shot of one of my share settings.  I know the cache drive is being used when I write to a share because it's the only drive that spins up and I can see the continuous writes on the web gui.  I've tried to read all I can to figure this out.  The thing that is really confusing is why writing directly to the cache drive is so much faster?  I've read somewhere that it would be faster but that much?

Untitled.jpg.36ab1a1bce2e7bad58a8d404c66c618b.jpg

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Writing directly to the cache drive is faster because it is outside of the protected array, meaning parity doesn't have to be calculated and written. The overhead of calculating and writing parity is what slows down writes to the array.

 

Yes I understand that but I'm comparing writing to the cache drive vs a cache enabled share which should basically be the same.  There's no parity calculated in either case.

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Writing directly to the cache drive is faster because it is outside of the protected array, meaning parity doesn't have to be calculated and written. The overhead of calculating and writing parity is what slows down writes to the array.

 

Yes I understand that but I'm comparing writing to the cache drive vs a cache enabled share which should basically be the same.  There's no parity calculated in either case.

 

Correct, they should basically be the same, I was simply replying to your question about "why writing to the cache drive is so much faster".

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Writing directly to the cache drive is faster because it is outside of the protected array, meaning parity doesn't have to be calculated and written. The overhead of calculating and writing parity is what slows down writes to the array.

 

Yes I understand that but I'm comparing writing to the cache drive vs a cache enabled share which should basically be the same.  There's no parity calculated in either case.

 

Correct, they should basically be the same, I was simply replying to your question about "why writing to the cache drive is so much faster".

 

my question was in reference to the OP. Thanks thou.

 

I will remove simple features and report back.  any other suggestions are welcomed.

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So I removed simplefeatures and it looks like my speeds have improved.  I'm now getting closer to 40MB/s when writing to a cache enable share but now I'm getting ~85MB/s when writing directly to the cache drive.  There has to be a reason for this huge difference.  I'm not asking for it to be the same but somewhere in the 60MB/s would be nice.  Can anyone shed some light on this?  I don't have any other plugins except unmenu.  I'll try updating to the current version of unraid tomorrow and see it that helps.

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  • 4 weeks later...

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