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Slow parity sync


levster

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Posted

This is my first parity sync since upgrading to version 6, and for the most part it was running at 35.5 MB/sec. Once down to the last two 3TB drives the speed bumped up to 61 MB/sec. On the unRAID 5.x the parity sync and checks were in the 90's for the most part. Nothing really has changed since 5.x other than one of my drives being taken out of the array. Any idea what could have caused this slowdown?

 

Thanks,

 

Lev

tower-diagnostics-20151003-1859.zip

Posted

Known issue with a single core celeron, if you can upgrade to any dual core cpu and you'll have speeds close to v5

 

Really? 6 is that much more taxing? I guess I can drop in an 8400 or q6600. It never even occurred to me that I may need more power!  ;)

Posted

V6 needs more horsepower, your cpu is probably pegged @ 100% during a parity check, any dual core will do but you might as well get the best one you can.

 

Right now, running at around 69 MB/sec CPU utilization is around 85%. So, would you go with a fast 2 core or a quad? Is V6 optimized for 4 cores?

Posted

It's only at 100% when it's reading all disks, when the speed was 35MB/s

I'll run a parity check after the sync, and then change for a different cpu and rerun parity check to see the difference.

  • 2 weeks later...
Posted

Well, after some back and forth, I've upgraded to an E8400 dual core. Currently running parity check and am rather disappointed with the present speed. It's 33.8 MB/sec. CPU utilization does not go above 45%, so why is the parity check still so slow?

Posted

That’s to slow for an e8400, if you didn’t change anything else in your config something else is going on.

 

I see your "md_sync_window" is set to 60, this is way too low, well below the default 384, wich is already low for some systems, try with the default value.

 

Posted

That’s to slow for an e8400, if you didn’t change anything else in your config something else is going on.

 

I see your "md_sync_window" is set to 60, this is way too low, well below the default 384, wich is already low for some systems, try with the default value.

 

Sorry for the noob question, but what is that setting and where do I find it?  What should it be optimally?

 

Posted

I changed the md_sync_window value to default (Not even sure how it was changed to 60. I never adjusted those values), and moved my parity drive off of the controller card and placed it on the native sata port. Now, after about 15 minutes of re-running the parity check the speed is up to the 80's. Pretty much where it was with v5.x

 

Thank you for the advice,

 

Lev

Posted

Good to know that it’s back to normal.

 

Try to keep your disks evenly distributed on both SASLPs as they are a somewhat bandwidth challenged, the bottom SASLP shares the DMI link with the on-board ports so for best results and in case you get more disks avoid more than 5 or 6 array drives on the top SASLP and more than 8 total on the bottom one + on-board ports.

 

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