On Wed, Mar 16 2011 at 8:02pm -0400, Mike Snitzer <snitzer@redhat.com> wrote: > On Wed, Mar 16 2011 at 7:11pm -0400, > Les Mikesell <lesmikesell@gmail.com> wrote: > > > On 3/16/2011 5:55 PM, Mike Snitzer 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 > > > > How does the kernel know about the physical_block_size when the > > device reports itself as 512? And they handle 512 byte writes, just > > very slowly. > > The drive exports the information as part of its response to the > IDENTIFY DEVICE (for ATA) or READ CAPACITY (for SCSI) command -- it > splits out the physical and logical block sizes along with other > attributes. The kernel's SCSI (and libata) layer issues these commands > to the drive. I just got Phillips' mail that the drive lies and reports 512/512. (and I read your mail too quickly). So yeah, the WD EARS drives are scary. Best for WD to defend or explain them. 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/
