New pool - ashift of 9

[Crispin]

Folks,


I have rebuilt my once-was 4 x 4TB WD Reds from RAIDZ1 to a mirrored/striped pair (based on conversation here)

I then got reading about the sector size and see that mine is showing 9 and not 12.
In @cyberjock's post he mentions that getting a 9 is "just weird". Well.... :)

Code:

[root@nas] ~# zdb | grep ashift
			ashift: 9

All disks are the same, WD Reds.
smartctl

Code:

=== START OF INFORMATION SECTION ===
Model Family:	 Western Digital Red
Device Model:	 WDC WD40EFRX-68WT0N0
Serial Number:	WD-WCC4E1824781
LU WWN Device Id: 5 0014ee 25f860a30
Firmware Version: 80.00A80
User Capacity:	4,000,787,030,016 bytes [4.00 TB]
Sector Sizes:	 512 bytes logical, 4096 bytes physical
Rotation Rate:	5400 rpm
Device is:		In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is:	Tue Nov  1 21:21:40 2016 GMT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

Sector Sizes: 512 bytes logical, 4096 bytes physical

So, why would mine be 9? I destroyed the previous pool, created a new one.
Can I change this in situ or do I need to rebuild again?
Does this and by how much lend towards my perceived performance problems?

System:

TIA
Crispin

 

[joeschmuck]

The performance gain would not be noticeable for changing the alignment on such a small pool but on the positive side you likely gains a tiny bit more storage space. I believe you would need to rebuild the pool and create it manually to get an ashift value of 12.

 

[Kevin Horton]

For what it's worth, my system reports an ashift value of 9 as well, with a pool composed of 5 x 4TB Reds. It is currently running FreeNAS-9.10.1-U2, but was running 9.3.1 when the pool was built.

 

[Crispin]

So, according to the other post and other bits I've read, FN should work out at install / pool creating time what the sector size is and act accordingly. Is it that this is not the case or something specific to the Reds?

 

[Mlovelace]

Folks,


I have rebuilt my once-was 4 x 4TB WD Reds from RAIDZ1 to a mirrored/striped pair (based on conversation here)

I then got reading about the sector size and see that mine is showing 9 and not 12.
In @cyberjock's post he mentions that getting a 9 is "just weird". Well.... :)

Code:

[root@nas] ~# zdb | grep ashift
			ashift: 9

All disks are the same, WD Reds.
smartctl

Code:

=== START OF INFORMATION SECTION ===
Model Family:	 Western Digital Red
Device Model:	 WDC WD40EFRX-68WT0N0
Serial Number:	WD-WCC4E1824781
LU WWN Device Id: 5 0014ee 25f860a30
Firmware Version: 80.00A80
User Capacity:	4,000,787,030,016 bytes [4.00 TB]
Sector Sizes:	 512 bytes logical, 4096 bytes physical
Rotation Rate:	5400 rpm
Device is:		In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is:	Tue Nov  1 21:21:40 2016 GMT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

Sector Sizes: 512 bytes logical, 4096 bytes physical

So, why would mine be 9? I destroyed the previous pool, created a new one.
Can I change this in situ or do I need to rebuild again?
Does this and by how much lend towards my perceived performance problems?

System:
View attachment 14473

TIA
Crispin

Since FreeNAS started booting off of zfs it seems that zdb uses /boot/zfs/zpool.cache by default. So, when you run the zdb command it only shows the freenas-boot pool. You will need to point it to /data/zfs/zpool.cache for non boot pools: zdb -U /data/zfs/zpool.cache

I'm guessing your main pool is being built with an ashift=12 but you're only seeing the boot pool which is ashift=9 by default.

 

[Kevin Horton]

Thanks @Mlovelace. This shows that my pool has a ashift=12, as expected.

 

[Crispin]

Thanks. Mine too says 12 now .

 

[joeschmuck]

Since FreeNAS started booting off of zfs it seems that zdb uses /boot/zfs/zpool.cache by default. So, when you run the zdb command it only shows the freenas-boot pool. You will need to point it to /data/zfs/zpool.cache for non boot pools: zdb -U /data/zfs/zpool.cache

I'm guessing your main pool is being built with an ashift=12 but you're only seeing the boot pool which is ashift=9 by default.

I love it when a plan comes together!

Thanks for the information.