Hello Torrey,
Monday, November 13, 2006, 5:07:02 AM, you wrote:
TM> Robert Milkowski wrote:
>> Hello Torrey,
>>
>> Friday, November 10, 2006, 11:31:31 PM, you wrote:
>>
>> TM> Robert Milkowski wrote:
>>
>>>>>> Also scrub can consume all CPU power on smaller and older machines and
>>>>>> that's not always what I would like.
>>>>>>
>>>>>>
>>>>>> REP> The big question, though, is "10% of what?" User CPU? iops?
>>>>>>
>>>>>>
>>>> AH> Probably N% of I/O Ops/Second would work well.
>>>>
>>>> Or if 100% means full speed, then 10% means that expected time should
>>>> be approximately 10x more (instead 1h make it 10h).
>>>>
>>>> It would be more intuitive than specifying some numbers like IOPS,
>>>> etc.
>>>>
>>
>> TM> In any case you're still going to have to provide a tunable for this
>> TM> even if the resulting algorithm works well on the host side. Keep in
>> TM> mind that a scrub can also impact the array(s) you're filesystem lives
>> TM> on. If all my ZFS systems started scrubbing at full speed - Because they
>> TM> thought they weren't busy - at the same time it might cause issues with
>> TM> other I/O on the array itself.
>>
>> Tunable in a form of pool property, with default 100%.
>>
>> On the other hand maybe simple algorithm Veritas has used is good
>> enough - simple delay between scrubing/resilvering some data.
TM> I think a not-to-convoluted algorithm as people have suggested would be
TM> ideal and then let people override it as necessary. I would think a 100%
TM> default might be a call generator but I'm up for debate. ("Hey my array
TM> just went crazy. All the lights are blinking but my application isn't
TM> doing any I/O. What gives?")
You've got the same behavior with any LVM when you replace a disk.
So it's not something unexpected for admins. Also most of the time
they expect LVM to resilver ASAP. With default setting not being 100%
you'll definitely see people complaining ZFS is slooow, etc.
--
Best regards,
Robert mailto:[EMAIL PROTECTED]
http://milek.blogspot.com
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