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Re: [linux-lvm] Advanced Format disks mixed with regular disks?



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.

--
  Les Mikesell
   lesmikesell gmail com


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