On Sun, Mar 16, 2014 at 08:51:46PM +1000, Matt Connolly wrote:
> I’m not trying to change the ashift of a pool, I’m trying to override the
> physical block size of a new 4k-sector sized device so I can attach it to an
> existing ashift=9 zpool.
>
> Perhaps I’m doing it backwards trying to add a 4k sector drive to a 512b
> sector pool, and the override only works the other way?
Is this a 4k disk, or a 512e disk? It is possible to send 512-byte
commands to a 512e disk; it is not possible to send them to a 4k disk.
So convincing sd that a 4k disk has 512-byte sectors is not likely to
lead to any good outcome. That's why you'll note the following code at
sd.c:4227:
if (strcasecmp(name, "physical-block-size") == 0) {
if (ddi_strtol(value, &endptr, 0, &val) == 0 &&
ISP2(val) && val >= un->un_tgt_blocksize &&
val >= un->un_sys_blocksize) {
un->un_phy_blocksize = val;
} else {
goto value_invalid;
}
...
So yes, this can be used only to increase the blocksize, not to decrease
it, for the reason described above.
> If that’s the case, I’m happy to zfs send to a new ashift=12 pool.
Recommended.
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