[OpenIndiana-discuss] Migrating root zpool from old disks to new one. only one system available

[Gary Gendel]

On 6/12/12 9:32 AM, Jim Klimov wrote:
> 2012-06-12 16:45, Gary Gendel wrote:
>> On 6/12/12 8:00 AM, Jim Klimov wrote:
>>>
>>> Did the 3TB disk also report to the OS that it uses 4k sectors?
>>> What ashift value is used by the pool, ultimately? Example:
>>> # zdb -l /dev/rdsk/c2t0d0s0 | grep ashift
>>>         ashift: 9
>>>         ashift: 9
>>>         ashift: 9
>>>         ashift: 9
>>>
>>> If your 4KB disks use ashift=9 it is possible to get problems
>>> worse than decreased performance ;)
>>
>> I'm a bit confused.  I checked my mirrored Seagate ST33000651AS 3TB
>> drives using this method and I see "ashift: 9".  I'm sure that the
>> Seagates told them it had 512 sectors, but I thought that you couldn't
>> see the whole 3TBs with 512 sectors.  I have these striped with a 1TB
>> mirrored drive in the pool and zpool list shows 3.62T which seems about
>> right.  Is my understanding flawed?
>
> I failed to find the specs on the Seagate site which would state
> that this model uses 512B or 4KB sectors, or the Advanced Format.
> I thought that only Hitachi Desk/Ultra-Stars had 3TB disks with
> 512B native sectors (and 4TB models are Advanced-Formatted too),
> but that is not definitive. Maybe Seagate did that, maybe not.
>
> As for "ability to see", that's related to the disk size and
> the partitioning table used (GPT vs. older MBR, which can only
> address 2TB max), and not to the native sector size.
>
> As for the striped pool size - it seems about right.
> My 3TB disk is 2.72T, so a 4TB set being 3.6T seems okay.
> The raid10 mix also can have mixed ashifts, i.e. using ashift=12
> for the 3TB disks and ashift=9 for 1TB disks, if that's configured.
>
> Is your 1TB disk mirrored? Otherwise its single failure can bring
> the whole pool down.

I have a pair of 1TB mirrored drives striped with a pair of 3TB mirrored 
drives.  It looks like I have access to all the available storage.  I 
was just confused at why I was seeing all of the 3TB drives if I had 
ashift=9.  The specs for the drive on Seagate indicate that it has 512 
sectors, but it supports Advanced 4k sectors.  It's not clear if that 
means I will get better performance if I use ashift=12 or not.

At this time I'm just happy that it's working error free and I've got 
full access to the drives.  I was just surprised when I saw it didn't 
have ashift=12.

Gary