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RE: Unable to mount and repair filesystems

To: Dave Chinner <david@xxxxxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: RE: Unable to mount and repair filesystems
From: Gerard Beekmans <GBeekmans@xxxxxxxx>
Date: Fri, 30 Jan 2015 00:04:21 +0000
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Thread-topic: Unable to mount and repair filesystems
<snip>

> Hence if the superblock is showing 25 AGs and the new ags from 4-25 are not
> found on disk then either:
> 
>       a) if the grow was very recent the storage is not obeying
>       cache flushes and hence breaking fundamental IO ordering
>       behaviour; or,
> 
>       b) if the growfs happened long ago, the storage has lost the
>       data that was written to stable media...


To answer both Dave and Eric in a single email:

The growfs happened about 1 month ago. The storage crash occurred yesterday so 
that would make me think enough time would have passed to commit that data to 
disk so it must be option b) above.

I think it's academic at this point but to answer the SAN questions that came 
up:

The NFS server is the SAN itself. The SAN software is Nexenta which provides 
various methods of accessing its data (NFS, SMB and iSCSI being the primary 
ones).  When the SAN crashed, there was no warning so the Hypervisors had their 
shared NFS storage disconnected and ultimately after a timeout, the VMs that 
were running from those NFS shares were shutoff.

Eric: agf 5, 6, 7 and beyond are also full of 0s. 1-4 don't appear to be.

Gerard

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