[linux-lvm] fsync() and LVM

[Charles Marcus]

On 3/14/2009 8:51 PM, Marco Colombo wrote:
> Stuart D. Gathman wrote:
>> On Sat, 14 Mar 2009, Dietmar Maurer wrote: 
>> It just means that write barriers won't get passed to the device.
>> This is only a problem if the devices have write caches.  Note 
>> that with multiple devices, even a FIFO write cache could cause 
>> reordering between devices (one device could finish faster than another).

> No, it's more than that. PostgreSQL gurus say LVM doesn't honor fsync(),
> that data doesn't even get to the controller, and it doesn't matter
> if the disks have write caches enabled or not. Or if they have battery backed
> caches. Please read the thread I linked. If what they say it's true,
> you can't use LVM for anything that needs fsync(), including mail queues
> (sendmail), mail storage (imapd), as such. So I'd really like to know.

Seeing as my /var (with both postfix & courier-imap using it for mail
storage) has been on lvm for almost 4 years, that would be news to me...

;)

-- 

Best regards,

Charles