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Parity drive speeds - need some clarity


docspectre

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I have been using unRaid for a few weeks. Pretty happy so need to add some more disks - upgrading parity and data.

 

Thought I bought 2x7200rpm disks, but the WD Red isn't Pro so it's 5900rpm. The other drive is 7200rpm. Both passed preclear.

 

Rebuilding my parity now on my HP Gen 8 without write cache enabled (because I haven't got a UPS ). Using the WD Red gives ~37mpbs speed. Not great. 

 

So, would I benefit from stopping the rebuild and changing to the 7200rpm as parity and 5900 for data? Main data is media storage and PC backups.

 

For future I intend to get another 7200rpm, which means that my options will be:

 

6tb 5900 parity

6tb 7200 data

6tb 7200 data

 

or 

 

6tb 7200 parity

6tb 5900 data

6tb 7200 data

 

Or should I find another use for the WD Red?

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1 minute ago, johnnie.black said:

That's normal with write cache disable, no point in getting different disks, it will be the same.

Thought so. I will have to look at UPS option and then enable write cache.

 

After the parity is built, do the different disk speeds between parity and data matter too much?

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Your parity drive has to be at least as large as a your largest data drive, and as a best practice it should be at least as fast as your fastest data drive.  That said, I'd probably wait until you get the new 7200rpm drive and then add it as parity when you do.  You won't notice much difference in the meantime.

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13 hours ago, tdallen said:

Your parity drive has to be at least as large as a your largest data drive, and as a best practice it should be at least as fast as your fastest data drive.  That said, I'd probably wait until you get the new 7200rpm drive and then add it as parity when you do.  You won't notice much difference in the meantime.

Yeah, I will have to wait until then - thanks. I'll probably get a UPS at the same time.

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I don't have a ups and run unRaid with default write cache settings. Power cuts are very rare, but they do happen once or twice a year. I used to get occasional sync errors when it happened, but have not seen one in ages. Even when I got the occasional sync error, I never had corruption on the data disk.

 

I'm not sure exactly what you disabled, but I'd go back to default settings.

 

My disk contains a mix of drives including slower WD REDS and parity build runs at about 140 MB/sec. 37 way too slow! 

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Sorry to piggy back off this thread but its pretty relevant. I had a power cut the other night as a bulb blew, I don't have a UPS so my server had unexpected shutdown. Parity disk was disabled so I started a parity sync again. Sync completed but drive is still disabled, any ideas what I can do? 

 

I need to get a UPS I know and I have write cache and turboboost enabled. Had power cuts before its been fine but this times something has gone wrong. Do I need to completely wipe the parity drive before re-sync? 

 

Diags attached. 

unraid-diagnostics-20180121-1121.zip

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6 minutes ago, johnnie.black said:

Since it's a MIcroserver and no cables to re-seat I would swap slots with a different disk and try again, in case it happens again see if it follows the disk or stays with the slot.

 

I am actually just in the process of building a new build so I could just take all the disks out and see if its fine in the new box? extended self-test currently running should I wait for this to complete or can I cancel it?

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1 minute ago, witalit said:

I am actually just in the process of building a new build so I could just take all the disks out and see if its fine in the new box?

yes

 

1 minute ago, witalit said:

extended self-test currently running should I wait for this to complete or can I cancel it?

as you prefer, since it doesn't take that long on a 2TB disk might as well let it finish

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1 minute ago, johnnie.black said:

yes

 

as you prefer, since it doesn't take that long on a 2TB disk might as well let it finish

 

Thanks man. Here is a link to my new build just for reference! Machine is built will be updating build log today, just waiting for the disks to be swapped. 

 

 

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