On Sat, Mar 30, 2013 at 07:49:54AM -0500, Stan Hoeppner wrote:
> On 3/19/2013 5:14 AM, Stan Hoeppner wrote:
> > On 3/19/2013 3:24 AM, Martin Steigerwald wrote:
> >> Heck, even I was confused at first. Cause the manpage of fsck.ext4 IMHO is
> >> not really clear about that topic to say the least. I tested it out for a
> >> reason.
> > I already contacted Ted off list hoping he can point me to the relevant
> > kernel documentation, so I don't make such a mistake again with EXT.
> Ok, so here's the skinny on the source of our confusion WRT how/when
> EXT4 replays journals, and it's rather interesting. Ted Ts'o explained
> the following.
> The EXT4 kernel module does have code to perform journal replay, but it
> is rarely executed. The reasons for this are:
> 1. EXT4 journal replay can take a lot of time (whereas XFS is instant)
19 minutes is my current record for XFS journal replay. 2GB log,
filled full of inode creates, required about 300,000 IOs to complete
> 2. EXT4 systems tend to have multiple filesystems, often one per drive
> (whereas XFS systems tend to have few filesystems)