ZFS Why would zfs-managed files migrate? And why to a ufs disc?

MMacD

MMacD

When I installed 10.2 on my server-of-all-work, I included ZFS to manage 2 3-way mirrors. It seemed to work very well except for parts of subtrees being duplicated without warning elsewhere in the pool. I was busy, and it seem annoying rather than harmful, so I didn't investigate.

Yesterday the server had a total hang. Before I brought it back up this morning, I disconnected the zpool drives to keep them unaffected by anything crazy that might happen.

But I just noticed that there are bits of the zpool, presumably copies, that somehow migrated to the root filesystem (ufs, separate hardware).

Has anyone else experienced anything like that? If so, did you figure out what causes it?
 
MMacD said:
It seemed to work very well except for parts of subtrees being duplicated without warning elsewhere in the pool.
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That makes no sense; ZFS does not copy data to other places in the directory tree, or migrate it. This must have been done by some process.

But I just noticed that there are bits of the zpool, presumably copies, that somehow migrated to the root filesystem (ufs, separate hardware).
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The system (OS and file system) itself won't do that. But this can happen easily if a file system is mounted and unmounted. For example: You usually have /mnt/foo is a mount point, and you "mount /dev/xxx /mnt/foo", and write files to there: they will end up in the mounted file system. Then you unmount the file system, but some process continues to create files: those will end up in the underlying file system. Now, depending on whether the file system is mounted or not, two different and separate sets of files will be visible: big mess.
 
ralphbsz said:
This must have been done by some process.
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Or some person. MMacD does anyone else have access to the machine that could possibly have messed it up?

ralphbsz said:
Then you unmount the file system, but some process continues to create files: those will end up in the underlying file system.
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This has bitten me more than once too. Easy to overlook and make that mistake.
 
SirDice said:
Or some person. MMacD does anyone else have access to the machine that could possibly have messed it up?
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I don't think so. Certainly not with permission. I have a pfsense firewall box with snort sitting at the entrance to the lan, and the rules for the outside nic are the default ones: no entry. My password isn't in any language a cracker would be likely to know\, but anyone who could get past the firewall could break it with a rainbow table easily enough. And of course if they could get physical access they could do whatever they liked.
 
ralphbsz said:
When I said "process", I didn't necessarily mean an unintended process that runs automatically; it could easily be a human that is logged in and doing these operations manually (with the "process" here being their shell).
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I'm sure that explains how these scraps wound up in the root filesystem, though I'd expect them to be underneath the mount points, not directly under / itself.

But the "more wierder" thing is finding pieces copied within the zpool's space. As an example, one of the pools is named /files (creative name). Under it are other subtrees (which, for some reason, I also allocated as zfsfilesystems) 2 of which are called 1Compu and 4Pers for computer-related and personal files respectively. One day I noticed that 4Pers had a piece of 1Compu in it. How did it get there? No clue. And there's a piece of 4Pers in the AandC space. Again, no clue.
 
MMacD said:
But the "more wierder" thing is finding pieces copied within the zpool's space. As an example, one of the pools is named /files (creative name). Under it are other subtrees (which, for some reason, I also allocated as zfsfilesystems) 2 of which are called 1Compu and 4Pers for computer-related and personal files respectively. One day I noticed that 4Pers had a piece of 1Compu in it. How did it get there? No clue. And there's a piece of 4Pers in the AandC space. Again, no clue.
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I fear the only way to explain this is user error, meaning things the user did but didn't intend to do. Perhaps you should review things like whether you use file manager applications on a GUI and sometimes click in strange places, or use wildcards on the command line in unusual fashions. The file system will not do these kinds of things by itself.
 
That was my take on it too: that I'm doing something that I don't realise I'm doing. But I can't work out what it can be.
 
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