[zfs-discuss] raidz1 or raidz2

Niels de Carpentier zfs at decarpentier.com
Tue Nov 6 09:27:29 EST 2012


Gordan Bobic wrote:
> On 11/06/2012 08:42 AM, Nyamul Hassan wrote:
>> On Tue, Nov 6, 2012 at 2:36 PM, Erik Koennecke <ekoennecke at gmail.com
>> <mailto:ekoennecke at gmail.com>> wrote:
>>
>>     I just replaced the disks in an 8 x 2 TB RAIDZ2 pool with 4 TB
>>     disks; my experience: first disk took 31 hours, the last one took 16
>>     hours (the others almost linear in between). Load was very light on
>>     the system, but the pool was 95% full.
>>
>>     Why should the resilvering take so long? For me, the whole pool was
>>     rotated with new disks after just a little more than a week.
>>
>>     Erik Koennecke
>>
>>
>> Could it be, that the available RAM and CPU has an impact on how long it
>> takes to rebuild an HDD?
>
> Not if your CPU is mostly idle and iostat is showing the disks to be
> churning out as many IOPS as their rotational latency allows.

But disks don't need to do IOPS for data that is already cached, so the amount of available RAM will have an impact on the resilvering time.

Niels



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