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Re: RFE: mount newly formatted volumes with barrier=0

On 01/03/2011 11:03 AM, Avi Kivity wrote:
> On 01/03/2011 06:56 PM, Eric Sandeen wrote:
>>>  Sure.  I imagine we'll see measurable benefit since installs are
>>>  metadata intensive.
>> Yeah, it should be a win.
>> Switching off barriers for a -freshly-made- filesystem is fine with me.
>> Just need to be 100% sure that it doesn't persist in fstab, and that we
>> do not mount -existing- filesystems with barriers off.
> I don't know the anaconda code, but I'd go for mounting normally, then 
> issuing a 'mount -o remount,barrier=0' to disable barriers for the 
> duration of the install.

One other thing that will need to be added, I think, is a way to flush
drive caches when it's all done.  (Ric pointed this out).

Otherwise you'll have fresh data/metadata sitting in a drive cache
post-install, and what happens when you reboot?  How lucky do you feel? :)

We'll need to do a quick mount/unmount with barriers, or an explicit
cache flush of the device via the blkdev tool, or something, to
guarantee that all the install data is safely though the cache and on disk.


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