Re: [LSF/MM TOPIC] linux servers as a storage server - what'smissing?

[Ric Wheeler <rwheeler@redhat.com>]

On 01/26/2012 05:24 PM, Dave Chinner wrote:
> On Tue, Jan 24, 2012 at 12:05:23PM -0500, Loke, Chetan wrote:
>>>> But writes that have to fetch the non-cached data, will
>> unnecessarily
>>>> issue I/O to the fabric. These orphaned I/O's cause more pain in the
>>>> cleanup.
>>>> And if caching is enabled on the front-side then it's all the more
>>>> painful.
>>>>
>>>> We can go one extra step and make FS fail read I/O for non-cached
>> data
>>>> too to avoid more orphan IOs.
>>> I don't really see this as a useful state. Read-only without a real
>>> backing file
>>> system or LUN is hit or miss, that file system should go offline :)
>>>
>> Last year when I checked, I forget but I think xfs(or ext4) was going
>> read-only.
>> If this is still the case then you are basically asking FS's to modify
>> that behavior.
> ext4 goes read only on erro by default. I think that behaviour can
> be changed by a mount option.
>
> XFS shuts the filesystem down (takes it offline) preventing all
> dirty data and metadata from being issued to disk, aborts any
> journal IO that might be going on, etc. It the returns fatal errors
> (EIO or EUCLEAN "structure needs cleaning" errors) to all callers
> that attempt to write or modify the filesystem, and EIO to all
> attempts to read from it.
>
> IOWs, the XFS filesystem is *gone* once it shuts down and requires
> administrator intervention to get it back to a working state....
>
> Cheers,
>
> Dave.

If it isn't obvious, I like the XFS approach :)

Ric