On Thu, Jan 26, 2012 at 05:29:03AM -0700, Andreas Dilger wrote: > > Ext4 will also align IO to 1MB boundaries (from the start of > LUN/partition) by default. If the mke2fs code detects the > underlying RAID geometry (or the sysadmin sets this manually with > tune2fs) it will store this in the superblock for the allocator to > pick a better alignment. (Still in Hawaii on vacation, but picked this up while I was quickly scanning through e-mail.) This is true only if you're using the special (non-upstream'ed) Lustre interfaces for writing Lustre objects. The writepages interface doesn't have all of the necessary smarts to do the right thing. It's been on my todo list to look at, but I've been mostly concentrated on single disk file systems since that's what we use at Google. (GFS can scale to many many file systems and servers, and avoiding RAID means fast FSCK recoveries, simplifying things since we don't have to worry about RAID-related failures, etc.) Eventually I'd like ext4 to handle RAID better, but unless you're forced to support really large files, I've come around to believing that n=3 replication or Reed-Solomon encoding across multiple servers is a much better way of achieving data robustness, so it's just not been high on my list of priorities. I'm much more interested in making sure ext4 works well under high memory pressure, and other cloud-related issues. - Ted -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
