Re: [vserver] Possible Hashify Corruption

From: Gordan Bobic <>
Date: Sun 17 Oct 2010 - 15:25:04 BST
Message-ID: <>

On 17/10/2010 14:54, Michael S. Zick wrote:
> On Sat October 16 2010, Gordan Bobic wrote:
>> Hi,
>> Can anybody hazard a guess as to what happened here? I'm prepared to
>> consider any theory at the moment, no matter how far fetched.
>> I'm running The file system is ext4
>> without journal and in data=writeback mode.
> Lets go with your first guess, file corruption, and speculate a bit...
> We know that ext4 gets its speed by the high degree of meta-data and
> data catching that it uses.
> We know that if ext4 is not cleanly shut down, your file system is
> burnt toast.
> On any type of system.

That is, in my experience, superstition. I have a number of laptops with
SSDs where I don't want the write overheads of journalling with the
exact same setup, and none have ever had any file corruption issues.
Sure, sometimes after yanking the battery the files that the open for
writing get broken and fsck puts their fragments in lost+found, but
that's no worse than ext2 has been before it.

> Now, can we relate those behaviors to a single file system name space?
> Or, first, was it limited to a single file system name space?

Yes - there is only one partition, only one file system (the root one).

> Was the guest you where running and changing file content on the __only__
> one that may have had changed files?

Both guests are toast in exactly the same way. The host's binaries are
fine and the host boots OK. The guests were running fine for days, with
many guest reboots in the meantime. Things appear to have gone wrong
when the host was shut down. That _might_ imply that things were running
fine from the caches pre-filled some time before, but it seems really
strange that ALL binaries would be hosed, even the ones that were never
touched. The only thing that would have touched them all that I can
think of is hashify.

> That one is a slim chance, the host context is writing to /var/log/* if
> nothing else - any of those get corrupted?

My /var/log is on tmpfs in both the host and the guests (I'm on a SSD
and don't need the logs so I don't want them wasting my write cycles).

> Where there other running guests on the system, with changed / changing files
> that did not get corrupted?

There are only two guests on the system, and they were both running.

> Did you shut down just this one guest or the entire machine?

First the guests individually, then the host machine. Clean shutdowns.

> Are you using tagging on this file system?

Tagging? What do you mean?

> Sorry for only having questions rather than answers.

Questions are good, too. Right now I'm out of ideas so anything that
comes up with possibilities is good.

Received on Sun Oct 17 15:25:16 2010

[Next/Previous Months] [Main vserver Project Homepage] [Howto Subscribe/Unsubscribe] [Paul Sladen's vserver stuff]
Generated on Sun 17 Oct 2010 - 15:25:16 BST by hypermail 2.1.8