On Jun 24, 2010, at 10:42 AM, Robert Milkowski <mi...@task.gda.pl> wrote:

> On 24/06/2010 14:32, Ross Walker wrote:
>> On Jun 24, 2010, at 5:40 AM, Robert Milkowski<mi...@task.gda.pl>  wrote:
>> 
>>   
>>> On 23/06/2010 18:50, Adam Leventhal wrote:
>>>     
>>>>> Does it mean that for dataset used for databases and similar environments 
>>>>> where basically all blocks have fixed size and there is no other data all 
>>>>> parity information will end-up on one (z1) or two (z2) specific disks?
>>>>> 
>>>>>         
>>>> No. There are always smaller writes to metadata that will distribute 
>>>> parity. What is the total width of your raidz1 stripe?
>>>> 
>>>> 
>>>>       
>>> 4x disks, 16KB recordsize, 128GB file, random read with 16KB block.
>>>     
>> From what I gather each 16KB record (plus parity) is spread across the raidz 
>> disks. This causes the total random IOPS (write AND read) of the raidz to be 
>> that of the slowest disk in the raidz.
>> 
>> Raidz is definitely made for sequential IO patterns not random. To get good 
>> random IO with raidz you need a zpool with X raidz vdevs where X = desired 
>> IOPS/IOPS of single drive.
>>   
> 
> I know that and it wasn't mine question.

Sorry, for the OP...


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