Suggestions on keeping cold spare or use 2nd parity

[gentux]

Hi there

 

I've successfully merged all my distributed network storage to a Ryzen 5800X based Unraid server. Before it had 2 x 2TB data + 1 x 2TB parity now it has 6 x 18TB + 1 x 18TB parity drive. The array is at 64% storage utilization. I now have one last 18 TB drive which I'm currently preclearing to check for any errors.

 

Would you add this one as parity 2 or pack it up and store it safely as a cold spare?

 

If I were to use it as Parity 2 I should search some 5.25 inch brackets as my 4U rack case has only space for 7x 3.5inch drives. But I'm not sure if there's an advantage of having a 2nd parity vs beign able to quickly replace a failed drive?

 

[JonathanM]

Do you have notifications set up? Do you get daily status reports from the server? Can you act on any warnings promptly?

 

If yes, cold spare.

If no, 2nd parity, and work on the notifications aspect.

 

A second parity could be useful to buy some time in certain failure modes, but with only 6 data drives it feels wasteful to me to keep it powered.

[gentux]

For the moment I look onto the dashboard at least once a day but notifications are the next thing I'll set up. Thank you for your advice.

Edited August 19, 2022 by gentux

[JonathanM]

3 hours ago, gentux said:

The array is at 64% storage utilization.

Personally I like to run a little closer, within reason. I like to keep between 1 and 2X the size of my largest data drive free, so in your case with 6 equal data drives I'd want between 66% and 80% used, and add or upgrade drives to get back into my sweet spot. Extra spindles = heat, energy, failure risk

[gentux]

17 hours ago, JonathanM said:

Personally I like to run a little closer, within reason. I like to keep between 1 and 2X the size of my largest data drive free, so in your case with 6 equal data drives I'd want between 66% and 80% used, and add or upgrade drives to get back into my sweet spot. Extra spindles = heat, energy, failure risk

Good catch! Actually I double checked because 64% seemed not enough and then discovered I did one HUGE mistake with the share cache settings and deleting files because it was so full it mounted read-only and me thinking it wasn't able to delete files that should've been copied back to array when I actually set it to move from array to cache... Luckily old unRAID disks can be remounted easily after changing UID with btrfstune and files restored with rsync. Now I'm at 66% and the mover is doing the right thing keeping the cache low and only keeping appdata in there.

[MrGrey]

Backup?... I'm so stupid, I assume everyone has one.

 

Parity is to ensure things keep working right now. Backup is to ensure things keep working forever.

 

MrGrey.

[gentux]

@MrGrey of course, Backups are a different thing to me and were never part of this discussion. I'm working on an external 8-bay thunderbolt box but I can't get it to show up yet but that would be my backup destination.

 

For now I have a perfect backup thanks to the migration.

 

I was just curious if 2nd parity would give me quality of life improvements over those that come with having peace of mind when 2 data drives failing simultaneously.

[ConnerVT]

Jonathan talked me out of using dual parity, and saving the drive for a cold spare.  He takes the fun out of compulsive excessive hardware. 

 

But seriously, if you have brand new DC550 drives and a solid build, and aren't always messing around with it, it is unlikely you are going to have multiple drive failures.

[JonathanM]

4 minutes ago, ConnerVT said:

if you have brand new DC550 drives and a solid build, and aren't always messing around with it, it is unlikely you are going to have multiple drive failures.

Unless all the brand new drives happened to be in the same box that fedups kicked across the warehouse.

 

Never source multiple drives at the same time if you can help it.

[ConnerVT]

I did say you take all the fun out of compulsive excessive hardware. 

 

For my case, drives did mostly come from same supplier, but at different times.  I did run dual parity for about a month, as I wanted to see what, if any, difference to performance it made.  (note: Not much at all, even with a 1st gen Ryzen 4c/8t).  I then pulled it out of the Parity 2 slot, precleared it, boxed it back up and put it in a drawer of the desk the server sits on.

 

Later, I bought some 8TB drives, 2 I installed, and the third sits next to the 6TB from before.  When I need some more space (I'm just under 60% now) I'll add the 6TB.