I'd like to do a parity check and not a sync, but I think there's no automated way to do that through the GUI.  Any suggestions?

Click the check button.... Bad advice don't do it!

The other alternative would be to log into the console as root and execute

/root/mdcmd check NOCORRECT

If you do from the console you should log into the physical console (IPMI, KVM, real keyboard/monitor) or use screen if you are telnetting in to prevent it getting clobbered if you lose connection.

I'd like to do a parity check and not a sync, but I think there's no automated way to do that through the GUI.  Any suggestions?

The stock GUI does not have a way to do a "check" only.

 

The add-on unMENU GUI does have a way to perform a "readonly" check.

 

If you have it installed it is as easy as clicking on one button.

 

Just be aware... the stock GUI will still "say" the errors are corrected, even if actually performing the read-only check.  It was never updated to be aware of the read-only function so it acts identically and says the same things regardless of checking vs. syncing.

 

Do NOT click on the "Check" button as previously instructed, as that will sync and correct parity based on what it is reading from the disks.  If you had a bad disk it would ruin your chances of fixing the disk by reading the "correct" parity.

 

Joe L.

Click the check button....

This is actually a "Sync" button if any descrepncies are found. It is NOT what you want to do if you suspect a disk is failing.

The other alternative would be to log into the console as root and execute

/root/mdcmd check NOCORRECT

This is correct advice.

If you do from the console you should log into the physical console (IPMI, KVM, real keyboard/monitor) or use screen if you are telnetting in to prevent it getting clobbered if you lose connection.

It does not matter where you type the command.  You do not need to stay logged in for its duration.

 

Joe L.

Updated my original post to remove bad info!

 

So the button that says check actually performs a sync???  That's kind of VERY misleading.......

The default parity check is a 'check and correct', so it will correct any parity errors that it finds on the fly, always assuming that the data drive has the good data and the parity drive has the bad data.  If you have a failing parity disk, then this may be what you want unRAID to do.

 

However, if a data disk is failing and spitting out bad data, a parity check will actually cause the otherwise good data on the parity drive to be overwritten with bad data from the failing disk.  This is why you should always run a 'parity verify' (check but do not correct) from unMenu or from the command line if you suspect a disk may be bad.

 

I agree that it is misleading, and I and others feel that the default option on the unRAID GUI should be the safer parity verify, with parity check being a 'I'm sure I want to do this' type of sub-option.

Hmphhh one more thing to worry about!

I decided to tinker with greasemonkey a bit, (javascript is a PITA!) but I managed to knock out a simple script that will add a big red warning about that button!  And for fun I made it add a link to unMENU on the main nav bar.  Fancy right?  

 

Here is the script if anyone is interested

// ==UserScript==
// @name          Spectrum's unRAID Fixes
// @namespace     http://null
// @description	  Fixes bad things in the unRAID configuration pages 
// @include       http://tower/*
// ==/UserScript==

// Warn about the stupid check button
document.body.innerHTML= document.body.innerHTML.replace(/<td valign="top" width="60%"><strong>Check<\/strong> will start  a Parity-Check.<br>/g,"<td valign=\"top\" width=\"60%\"><strong>Check<\/strong> will start  a Parity-Check and Correct. <font color=red><strong>Do NOT use this if you think a disk is failing!</strong></font><br>");

// Lets add a menu item for unMenu
document.body.innerHTML= document.body.innerHTML.replace(/<a href="devices.htm">Devices<\/a><\/td>$/m,"<a href=\"devices.htm\">Devices<\/a> | <a href=\"" + location.protocol + "\/\/" + location.host + ":8080\">unMENU</a><\/td>");
document.body.innerHTML= document.body.innerHTML.replace(/<strong>Devices<\/strong><\/td>$/m,"<strong>Devices<\/strong> | <a href=\"" + location.protocol + "\/\/" + location.host + ":8080\">unMENU</a><\/td>");

// Thats all for now!

 

It's a Greasemonkey script so you need Greasemonkey. Firefox Chrome Opera IE (only tested in FF)

 

Copy and paste into a text editor.  Change tower in the  // @include       http://tower/* line to your server name or IP address (you can add more @includes if you use name and IP addresses or have multiple unRAID servers) and save as the file as spectrums_unraid_fixes.user.js.  Then drag the script onto the browser window and click on install.