If a block device is presented with 512 sectors on 4k-only sector
drives, then that's a bug. If it's doing so with 512e drives,
then that's still a bug because it should be presenting as a
512 byte logical, 4096 byte physical sector size device and in that
case mkfs.xfs will choose 4k sectors by default.
IOWs, if the underlying device is correctly presented to mkfs.xfs
then it will choose the correct sector size by default. dm-thinp
does the right thing with sector sizes, but I have no idea about
ZoL.
Hi Dave,
it seems ZVOLs behave... interestingly...
# 4K volume
[root@blackhole ~]# zfs create tank/vol1 -V 300M -b 4k
[root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt
/dev/zvol/tank/vol1
512
4096
4096
4096
# 8K volume
[root@blackhole ~]# zfs create tank/vol1 -V 300M -b 8k
[root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt
/dev/zvol/tank/vol1
512
8192
8192
8192
# 128K volume
[root@blackhole ~]# zfs create tank/vol1 -V 300M -b 128k
[root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt
/dev/zvol/tank/vol1
512
131072
131072
131072
So, it seems that volume's block size does not only change the
iomin/ioopt values, but pbsz also. On the other hand, ss is stuck at
512B, even if I am using a 512e (4K physical sector size) underlying
disk:
[root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt
/dev/sdc
512
4096
4096
0
Creating an XFS filesystem on such a ZVOL will issue the following
message:
"specified blocksize 4096 is less than device physical sector size 8192
switching to logical sector size 512"
In this case, should I specify block size (-b size=4k) at mkfs.xfs time,
or not?
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
GPG public key ID: FF5F32A8
--
To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
