On Wed, Mar 16 2011 at 4:45pm -0400, Phillip Susi <psusi@cfl.rr.com> wrote: > On 3/14/2011 1:17 PM, Mike Snitzer wrote: > > Both LVM2 and Device Mapper have been updated to accommodate stacking > > such a mix of drives. > > > > See this for a bit more detail: > > http://people.redhat.com/msnitzer/docs/io-limits.txt > > > > Particularly, the "Stacking I/O Limits" section. > > > > The concern raised for partial (4k) writes to the 512b drive was > > discussed a bit more here: http://lkml.org/lkml/2010/2/22/295 > > Unfortunately this does not help with the WD EARS model drives ( are > there any other 4kb sector drives on the market now? ), since they lie > and report that they have 512 byte sectors. I'm not following what you're saying. The kernel's blk_stack_limits() infrastructure accounts for "desktop" class 4K devices too (4K physical, 512b logical) -- as does DM and lvm2. If given: "desktop" class drive: physical_block_size=4096 logical_block_size=512 minimum_io_size=4096 optimal_io_size=0 conventional 512 drive: physical_block_size=512 logical_block_size=512 minimum_io_size=512 optimal_io_size=0 Stacking these drives would result in a logical device that has: physical_block_size=4096 logical_block_size=512 minimum_io_size=4096 optimal_io_size=0 And yes, there are native 4K "enterprise" class drives (4K physical, 4K logical) in the market. Mike _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
