[gpfsug-discuss] Migration to separate metadata and data disks

[Miroslav Bauer]

Hello,

I have a GPFS 3.5 filesystem (fs1) and I'm trying to migrate the
filesystem metadata from state:
-m = 2 (default metadata replicas)
- SATA disks (dataAndMetadata, failGroup=1)
- SSDs (metadataOnly, failGroup=3)
to the desired state:
-m = 1
- SATA disks (dataOnly, failGroup=1)
- SSDs (metadataOnly, failGroup=3)

I have done the following steps in the following order:
1) change SATA disks to dataOnly (stanza file modifies the 'usage' 
attribute only):
# mmchdisk fs1 change -F dataOnly_disks.stanza
Attention: Disk parameters were changed.
   Use the mmrestripefs command with the -r option to relocate data and 
metadata.
Verifying file system configuration information ...
mmchdisk: Propagating the cluster configuration data to all
   affected nodes.  This is an asynchronous process.

2) change default metadata replicas number 2->1
# mmchfs fs1 -m 1

3) run mmrestripefs as suggested by output of 1)
# mmrestripefs fs1 -r
Scanning file system metadata, phase 1 ...
Error processing inodes.
No space left on device
mmrestripefs: Command failed.  Examine previous error messages to 
determine cause.

It is, however, still possible to create new files on the filesystem.
When I return one of the SATA disks as a dataAndMetadata disk, the 
mmrestripefs
command stops complaining about No space left on device. Both df and mmdf
say that there is enough space both for data (SATA) and metadata (SSDs).
Does anyone have an idea why is it complaining?

Thanks,

--
Miroslav Bauer


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