Author Topic: not enough usable space for parity  (Read 1492 times)

Offline alexktz

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not enough usable space for parity
« on: January 04, 2013, 07:13:37 pm »
hi,

first post. go easy!

long time user of unraid jumping in head first. i had a very limited amount of time to create this snapshot raid whilst at parents house this week for them and i fear i've done things too quickly without reading properly first. anyway, here goes.

i created a 3x 2tb drive snapshot array using 1x 2tb for ppu and 2x 2tb for dru. when i click on the button that says 'update' i get the error in screenshot 2. 'invalid state: not enough usable space for parity! Space need: (big bytes number which equates to roughly 1.6TB). The PPU drive has enough space to my belief (see screenshot 1).





What have I done wrong? I click verify and the system tells me everything is great, validate is also successful too. Only 'update' causes me issue.

Offline alexktz

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Re: not enough usable space for parity
« Reply #1 on: January 05, 2013, 06:16:42 am »
noone? i'm thinking there must be a simple solution to this problem, but i'm blinded by newness. please help me?

Offline lrissman

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Re: not enough usable space for parity
« Reply #2 on: January 05, 2013, 06:31:31 am »
First, remember this is a user forum and that we helpful users are not all on this 24/7, so posting at 8pm at night and expecting a full and comprehensive answer at 7am the next morning might be a bit on the wishful thinking side.

Having said that, I am not that familiar with Snapshot raid interface, but I read that you have 2 disks spanned into DRU1 for a total size of just under 4TB and a single PPU just under 2TB, so yes, your PPU is too smal..

I would recommend that you delete that configuration (your data will not be deleted), re-create a new snapshot, and dont use spanning.  Make each of your data disks a seperate DRU (DRU1, and DRU2).

Wiki will help:  http://wiki.flexraid.com/2011/12/03/getting-started-creating-your-first-flexraid-configuration/

Remember to choose DRU not Span into DRU# when you are adding the 2nd disk.

Offline alexktz

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Re: not enough usable space for parity
« Reply #3 on: January 05, 2013, 06:33:49 am »
THANK YOU!!!!

obvious to old timers perhaps, but that just didn't make itself obvious enough to me in the documentation on the wiki. i didn't notice the forum was on US time, I'm on UK time so maybe that's the source of my petulant impatience!

anyways, thank you for your simple and straightforward answer. i'll do that now.


Offline lrissman

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Re: not enough usable space for parity
« Reply #4 on: January 05, 2013, 06:42:12 am »
Glad I could help!    that is one of the first things I found coming to flexraid from long-time user of traditional raid.   It is different, and it takes a bit to get used to all the terms and helpfulness. 

Also, for me the forum isn't on US time, it is on Canadian time.. ;-)    (Although, I do think most of the users here are from my neighbours in the USA)

Offline alexktz

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Re: not enough usable space for parity
« Reply #5 on: January 05, 2013, 07:09:26 am »
ok i'm going to hijack your attention whilst i have it too. going to be migrating my unraid box to a windows based flexraid later today and want to know the best arrangement of the following drives please...

4x 3TB
2x 1TB
1x 1.5TB

I have about 10TB of data to load the system with and will be again after snapshot. I'm thinking this...

PPU = 1x 3TB                       (3TB)
DRU1 = 1x 3TB                     (3TB)
DRU2 = 1x 3TB                     (3TB)
DRU3 = 1x 3TB                     (3TB)
DRU4 = 1x 1TB + 1x 1.5TB   (2.5TB)

this arrangement leaves 1x 1TB drive spare though. how much space will i have available with that above config? and is there any better way to arrange these drives to maximise space?

Offline lrissman

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Re: not enough usable space for parity
« Reply #6 on: January 05, 2013, 07:38:31 am »
No problem.

One of the biggest boons about flexraid is Flexability.  You dont have to match disk sizes. 

First thing I think you need to consider with 7 drives is if 1 unit of failure is sufficient for you.   I run 2 PPUs that way I can sustain a double disk failure. 

Next, your PPU(s) must be equal to your largest DRU.   what you have listed is fine, but it does show that at least one of your 3TB disks need to be in a PPU.

Beyond that, For simplicity i would simply create 1 disk per DRU -- easier to conceptualize when it comes to failure recovery.   What this does mean is that if you ever want to reduce the number of members in your array (eg, replace your 1.5 and 2 1TB disks with a larger disk) you will likely be up for removing your configuration and creating a new one.  (Note this wont affect your data, just your time as it would require a rebuild of your parity).

The benefit of spanning is that you can plan for future large-disk replacements.   The downside is that if you lose one of the disks in the span, you have lost the entire DRU and will need to recover the data somewhere.

Clear as mud?