Re: raid 10f2 vs 1 on 2 drives

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in my tests with a mysql and similar database scenarios where write /
read are near 50% / 50% (many updates/inserts and many selects) the
best raid is 1
where scenario is 10%write / 90% read
raid 10far is better (if not degraded or out of sync)


just two scenarios to help 'what's better'  question

2012/5/25 Bill Davidsen <davidsen@xxxxxxx>:
> William Thompson wrote:
>>
>> On Wed, May 23, 2012 at 12:36:12AM +0200, David Brown wrote:
>>>
>>> On 22/05/12 21:33, William Thompson wrote:
>>>>
>>>> I understand that raid 10 f2 is slower on writes due to the location of
>>>> the
>>>> 2nd copy.  My question is, if lots of writes are performed, could this
>>>> layout wearout the drives quicker than raid 1?
>>>
>>>
>>> No, wear is not going to be significantly different.
>>>
>>> You didn't say whether you are talking about hard disks (where
>>
>>
>> Sorry about that (Chief).  Yes, I was refering to hard drives.
>>
>>> location makes a difference, but "wear" on the drive motor is
>>> insignificant to the disk's expected lifetime), or flash disks
>>
>>
>> I was thinking about how much more head movement there would be to write
>> the
>> 2nd copy of the data.
>>
> There _is_ no extra head motion. The location of consecutive blocks is
> different on each drive, but as I read the mapping function the distance
> between blocks on the same drive will be about the same, so amount of head
> motion (both number and distance) is the same on each drive, but the
> location of that motion is not the same.
>
> One drive may be seeking at the outer edge of the platter while another
> seeks near the spindle, but there's the same amount of seeking on each.
>
>
> --
> Bill Davidsen <davidsen@xxxxxxx>
>  "We have more to fear from the bungling of the incompetent than from
> the machinations of the wicked."  - from Slashdot
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-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
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