On Wed, Nov 13, 2013 at 12:25:33PM -0600, Eric Sandeen wrote: > Pure RFC; this might be crazy. Here's the problem I'm trying to solve: > > Today, mkfs.xfs will select a 4k sector size for a 4k physical / 512 logical > drive. (that change was done by me). The thought was that it'd be an > efficiency gain to not make the drive do the (possible) RMW cycles on > 512-byte log IO, primarily. > > However, now this restricts all DIO to 4k alignment, not the otherwise- > possible 512. > > This came up when qemu-kvm, in cache=none mode, tries to boot off an > image hosted on such a filesystem, and its bios wants to do a 512 byte > direct IO read off the disk - it fails. > > But I'm wondering - the buftarg's bt_sshift and bt_smask are only used > in a few places. No need to mess with kernel code IFF we want to change that, just keep the sector size at 512 bytes and set a log stripe unit at mkfs time. I have to admit that I'm not really sure if that's what we really want, through. A drive that has a larger physical block size will need read-modify-write cycles internally, which we try to avoid. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
