[Lustre-discuss] [wc-discuss] Re: Random OST Numbers chosen in a stripe

[Cory Spitz]

Hi, Roger.

Forcing RR all the time by setting qos_threshold_rr to 100 still won't
necessarily allow sequential OST stripe placement.  There is a set order
when specifying a starting OST.  The following bugs track related issues
with stripe allocation.

bz 20844: Can round-robin allocation be based on ost number?
	- this one essentially asks if stripes can land on sequential
	  OSTs as you asked
bz 21528: round-robin allocation not working as expected when a start
	  ost index is specified.
	- this one tracks a bug where two stripes used the same OSS
	  when it should not
bz 18547: optimize QOS RR allocator
	- this one tracks enhancements to the stripe allocators

Thanks,
-Cory


On 08/01/2011 03:38 AM, Johann Lombardi wrote:
> On Fri, Jul 29, 2011 at 04:49:28PM -0400, Roger Spellman wrote:
>> For a different file:
>>
>>    obdidx           objid          objid            group
>>      13            6884         0x1ae4                0
>>      28            6880         0x1ae0                0
>>      44            6880         0x1ae0                0
>>      27            6880         0x1ae0                0
>>
>> Why is this?
>>
>> How can I control it to always be sequential?
> 
> It depends on the OST usage imbalance and you can tune the stripe allocation policy with qos_threshold_rr. For more information, please refer to the lustre manual:
> http://wiki.lustre.org/manual/LustreManual20_HTML/LustreProc.html#50438271_pgfId-1296529
> 
> Cheers,
> Johann