On 1/13/14, 3:16 PM, Benjamin LaHaise wrote: > On Mon, Jan 13, 2014 at 02:01:08PM -0700, Andreas Dilger wrote: >> Not to be flippant, but is there any reason NOT to just mount the >> filesystem with ext4? There are a large number of improvements in >> the ext4 code that don't require on-disk format changes (e.g. delayed >> allocation, multi-block allocation, etc) if there is a concern about >> being able to downgrade to an ext3-type mount in case of problems. > > I'm leaning towards doing this. The main reason for not doing so was > primarily that a few of the tweaks that I had been made to ext3 would > have to be ported to ext4. Thankfully, I think we're still in an early > enough stage of release that I should be able to do so. The changes > are pretty specific, mostly allocator tweaks to improve the on-disk > layout for our specific use-case. > >> There are further improvements in ext4 that can be used on upgraded >> ext3 filesystems if the feature bit is enabled (in particular extent >> mapped files). However, extent mapped files are not accessible under >> ext3, so it makes sense to run with ext4 w/o any new features for a >> while until you are sure it is working for you. > > I had hoped to use ext4, but the recommended fsck after changing the > various feature bits is a non-starter during our upgrade process (a 22 > minute outage isn't acceptable). I would never recommend the ext3-ext4 "tune2fs migration" - you'll end up with a really weird hybrid filesystems containing files with different capabilities, and missing many of the metadata layout improvements. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
