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 Post subject: Spare Disk on 3PAR-7400
PostPosted: Fri Oct 25, 2013 10:16 am 

Joined: Wed Sep 25, 2013 1:12 am
Posts: 3
Has anyone know how to find out the number of spare disks and its location in the system either in GUI or CLI?
Trying to get this info bu really nothing comes up... the closest one i can get is
cli% showsys -devtype SSD -space
System : 188416
Internal : 0
Spare : 188416
Used : 0
Unused : 188416
dividing the Spare by the Size of individual or single disk of 92GB gives me that I have 2 spares of SSD in the system.... but is there any easy way where to locate them?
thanks for any feedback


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 Post subject: Re: Spare Disk on 3PAR-7400
PostPosted: Fri Oct 25, 2013 1:15 pm 
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Joined: Tue Aug 18, 2009 10:35 pm
Posts: 1224
Location: Dallas, Texas
3PAR, XIV and Compellent technologies do not dedicate entire drives to spare. They distribute spare capacity across all drives. When a drive fails, its chunklets will be relocated/rebuilt across many different drives of spare space.

Try this command:


Code:
showspare - Show information about spare and relocated chunklets.

SYNTAX
    showspare [-used]

DESCRIPTION
    The showspare command displays information about chunklets in the system
    that are reserved for spares and previously free chunklets selected for
    spares by the system.

AUTHORITY
    Super, Service, Edit, Browse

OPTIONS
    -used
        Show only used spare chunklets.
        By default all spare chunklets are shown.

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The views and opinions expressed are my own and do not necessarily reflect those of my employer.


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 Post subject: Re: Spare Disk on 3PAR-7400
PostPosted: Fri Oct 25, 2013 2:03 pm 

Joined: Wed Sep 25, 2013 1:12 am
Posts: 3
Thanks for the reply Richard!
I guess if no entire drive is dedicated for spare, the spare size that i am seeing
was configured the first time the 3PAR was installed.
How is the spare size configured though?
Is this something not configurable at the console or cli?
Assuming we would want to increase the spare size and adding more drives.
I would appreciate much any comments on this.


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 Post subject: Re: Spare Disk on 3PAR-7400
PostPosted: Mon Jan 21, 2019 8:36 pm 

Joined: Mon Jan 21, 2019 8:32 pm
Posts: 2
Hi, sorry for reviving an old post.

Does this mean that as long disk failures are not simultaneously, theres enough time between disk failures to finish the rebuild and i have spare chunklets free, i can have multiple disk failures without losing the volumes?


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 Post subject: Re: Spare Disk on 3PAR-7400
PostPosted: Tue Jan 22, 2019 4:48 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 934
Location: Europe
sartg wrote:
Hi, sorry for reviving an old post.

Does this mean that as long disk failures are not simultaneously, theres enough time between disk failures to finish the rebuild and i have spare chunklets free, i can have multiple disk failures without losing the volumes?


Yes.

And when you've used up all your spare chunklets the system will use free chunklets if available. So as long as you have free space in the system, you can lose a huge amount of drives (as long as every rebuild is allowed to complete before the next failure).

Edit: as for simultaneous failures you are down to RAID level and failure domains (node pair unless filtered in CPG). So a 8 node system with RAID6 (and no HA cage), you could lose 8 drives (2 behind each node pair) without losing data as long as it's the "right" drives. With HA cage you could lose all drives in one cage per node pair....

On the other side, without HA cage and only RAID5, you also could get data loss on 2 simultaneous failures if it was the "wrong" drives (ie behind same node pair).... and even worse you could get a minor data loss with a single disk failure if you encounter an URE during rebuild (read 3PAR RAID6 whitepaper).

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 Post subject: Re: Spare Disk on 3PAR-7400
PostPosted: Tue Jan 22, 2019 10:08 am 

Joined: Mon Jan 21, 2019 8:32 pm
Posts: 2
Thank you MammaGutt, that gives me some peace of mind.


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