Parity Errors

[leedog99]

Hello, running 6.8.3, 1 parity, 4 data drives. Normally, parity check has 0 errors. Last few runs I am getting 135+ errors. Reading other posts, is it true there is no way to see what those errors are, that would not make sense? I looked in the log but was unable to find. There must be some way to read what the errors are so you can address them?

Also, is the only way to run mem tests from bios?

[trurl]

Go to Tools-Diagnostics and attach the complete Diagnostics ZIP file to your NEXT post in this thread. 

 

You run memtest from the Unraid boot menu 

[leedog99]

i attached the zip file, thx

tower-diagnostics-20200807-0057.zip

[trurl]

Parity is simply an extra bit that allows a missing bit to be calculated from all the other bits. That is basically all it is wherever it is used in computers and communications.

 

All parity check can tell is that the calculated parity from all the data disks doesn't match parity. No way to know from just that extra bit which disk might be out of sync. If you have no reason to suspect any particular disk, you have no choice but to correct parity.

 

SMART for all disks looks OK, and nothing about any problems communicating with any disks in that syslog.

 

However, there is this:

Jul 26 12:28:20 Tower emhttpd: unclean shutdown detected

On 7/27/2020 at 2:12 PM, leedog99 said:

Last few runs I am getting 135+ errors.

That number seems reasonable for unclean shutdowns. Why did you have an unclean shutdown?

 

Unclean shutdown results in non-correcting parity check. You have to run a correcting parity check to correct the parity errors it found. Then you should run another non-correcting parity check to make sure you don't still have some problem. Exactly zero parity errors is the only acceptable result, and if you don't get there you aren't finished.

 

[leedog99]

Thank you so much. At least now I understand what is happening. I believe that unclean shutdown was exactly what caused the errors to occur. I did not have a battery backup on the unraid server but now I will, my bad.

QUESTION - so if there were errors in the parity drive, why does it still say PARITY IS VALID? Wouldn't the errors prevent some data from being properly recovered? That message kind of gives false security.

[leedog99]

I am still getting errors, ata7 is my parity drive. I have attached latest log, any ideas? I ran parity with correction, then without. Got 0 errors first few times, then 1 error, then 4 errors. Any suggestions would be greatly appreciated.

tower-syslog-20200929-1448.zip

[JorgeB]

Run memtest.

[leedog99]

 ran memtest, 7 passes, no errors.

[JorgeB]

Please post the diagnostics: Tools -> Diagnostics

[leedog99]

tower-syslog-20200929-1448.zip

[leedog99]

tower-diagnostics-20201001-0900.zip

[civic95man]

diagnostics are after reboot so the logs don't show anything; however you appear to be running a Marvell controller which is known to cause issues and therefore is not recommended.  This is most likely the cause of the parity errors.  Best to replace that with a supported controller and then re-sync parity

Edited October 1, 2020 by civic95man

[JorgeB]

Yes, I wanted to see a syslog with multiple parity checks, before rebooting, that Marvell controller doesn't usually cause sync errors, but it's a possibility, and like mentioned not recommended anyway.

[leedog99]

so there is 1 disc using the pcie sata card, i believe that is ata4.01. Is the pcie sata card the card you are referring to as the marvell controller?

[civic95man]

2 minutes ago, leedog99 said:

so there is 1 disc using the pcie sata card, i believe that is ata4.01. Is the pcie sata card the card you are referring to as the marvell controller?

yes to both

[leedog99]

i looked at the sata card specs and there is nothing about marvell controller. When I order another card, any suggestions on how I can tell if its as marvell controller or not?

[civic95man]

If it's not explicitly called out as the chipset then you would have to search google for an answer.  The JMB585 based sata controller seems to be a reliable alternative. Otherwise you could look at the LSI series flashed to IT mode.