[gpfsug-discuss] Failure Group

Jan-Frode Myklebust janfrode at tanso.net
Fri Apr 1 20:04:58 BST 2016


Hi :-)

I seem to remember failure group 4001 was common at some point, but can't
see why.. Maybe it was just the default when no failure group was specified
? Have you tried what happens if you use an empty failure group "::", does
it default to "-1" on v3.4 -- or maybe "4001"?

You might consider changing the failure groups of the existing disks using
mmchdisk if you need them to be the same.


Pro's and cons of using another failure group.. Depends a bit on if they're
using any replication within the filesystem. If all other NSDs are in
failure group 4001 -- they can't be doing any replication, so it doesn't
matter much. Only side effect I know of is that new block allocations will
first go round robin over the failure groups, then round robin within the
failure group, so unless you have similar amount of disks in the two
failure groups the disk load might become a bit uneven.


  -jf


On Fri, Apr 1, 2016 at 1:04 PM, Jan Finnerman Load <jan.finnerman at load.se>
wrote:

> Hi,
>
> I have a customer with GPFS 3.4.0.11 on Windows @VMware with VMware Raw
> Device Mapping. They just ran in to an issue with adding some nsd disks.
> They claim that their current file system’s nsddisks are specified with
> 4001 as the failure group. This is out of bounds, since the allowed range
> is –1>–—>4000.
> So, when they now try to add some new disks with mmcrnsd, with 4001
> specified, they get an error message.
>
> Customer runs this command: mmcrnsd -F D:\slask\gpfs\gpfsdisk.txt
>
> [image: Description: cid:image001.png at 01D18B5D.FFCEFE30]
>
>
>
>
>
> His gpfsdisk.txt file looks like this.
>
> [image: Description: cid:image002.png at 01D18B5D.FFCEFE30]
>
>
>
>
>
> A listing of current disks show all as belonging to Failure group 4001
>
> [image: Description: cid:image003.png at 01D18B5D.FFCEFE30]
>
>
>
> So, Why can’t he choose failure group 4001 when the existing disks are
> member of that group ?
>
> If he creates a disk in an other failure group, what’s the pros and cons
> with that ? I guess issues with replication not working as expected….
>
>
> Brgds
>
> ///Jan
>
>
> Jan Finnerman
>
> Senior Technical consultant
>
>
> [image: CertTiv_sm]
>
>
> Kista Science Tower
>
> 164 51 Kista
>
> Mobil: +46 (0)70 631 66 26
>
> Kontor: +46 (0)8 633 66 00/26
>
> jan.finnerman at load.se
>
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>
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