[CentOS] Is ext4 safe for a production server?

Pasi Kärkkäinen pasik at iki.fi
Sun Dec 13 15:15:57 UTC 2009

On Fri, Dec 11, 2009 at 09:20:24AM +0800, Christopher Chan wrote:
> Mark Caudill wrote:
> > Christopher Chan wrote:
> >> Morten Torstensen wrote:
> >>> On 08.12.2009 13:34, Chan Chung Hang Christopher wrote:
> >>>>> Speaking for me (on Linux systems) on top of LVM on top of md. On IRIX
> >>>>> as it was intended.
> >>>>>
> >>>> That is a disaster combination for XFS even now. You mentioned some
> >>>> pretty hefty hardware in your other post...
> >>> If XFS doesn't play well with LVM, how can it even be an option? I 
> >>> couldn't live without LVM...
> >>>
> >> I meant it in the sense of data guarantee. XFS has a major history of 
> >> losing data unless used with hardware raid cards that have a bbu cache. 
> >> That changed when XFS got barrier support.
> >>
> >> However, anything on LVM be it ext3, ext4 or XFS that has barrier 
> >> support will not be able to use barriers because device-mapper does not 
> >> support barriers and therefore, if you use LVM, it better be on a 
> >> hardware raid array where the card has bbu cache.
> > 
> > Wait, just to be clear, are you saying that all use of LVM is a bad idea 
> > unless on hardware RAID? That's bad it if it's true since it seems to me 
> > that most modern distros like to use LVM by default. Am I missing something?
> > 
> Yes, the Linux kernel has long been criticized for a fake 
> fsync/fsyncdata implementation. At the latest, since 2001. Unless you 
> had your hard drive caches turned off, you were at risk of losing data 
> no matter what you used: ext2, ext3, reiserfs, xfs, jfs, whether on lvm 
> or not.
> Write barriers were introduced to give data guarantees with hard drives 
> that have their write cache enabled. Unfortunately, not everything has 
> been given barrier support. LVM and JFS do not have write barrier support.


"Barriers are now supported by all the types of dm devices."

-- Pasi

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