ZFS and 4k sector drives

[Ivan Voras]

On 11/15/10 20:24, Wojciech Puchar wrote:
>> work with ZFS raidz2 pools. It seems that most of the 4k sector drives
>> are using emulation, and reporting 512 byte sectors to the OS instead
>> of their native 4k size. I know someone who had an issue trying to
>> insert one of these drives into a running ZFS pool with other 512 byte
>> sector drives with bad results.
>
> ZFS use 4k blocks.

Actually, no, it's much worse: ZFS uses variable block size upto 128 
KiB, meaning not only does it not write or align data on a sensible 
boundary like 4 KiB, both its metadata and data IO can write on any 
offset and length which is a multiple of 512 bytes.

References:

http://www.solarismen.de/archives/5-Solaris-and-the-new-4K-Sector-Disks-e.g.-WDxxEARS-Part-2.html

http://permalink.gmane.org/gmane.os.freebsd.devel.geom/4318