Re: stripe_cache_size and performance

[Justin Piszcz <jpiszcz@lucidpixels.com>]

I repeat: what does the patch do (or is this no longer applicable)?

This was for if your stripe_cache_size was above a certain number, it 
would run at 1-3MB/s rebuild speed.  You can always force with the min 
parameter.  Forcing it you should get good speed, faster than 1-3MB/s 
anyway :)

Justin.

On Tue, 26 Jun 2007, Jon Nelson wrote:

> On Tue, 26 Jun 2007, Justin Piszcz wrote:
>
>>
>>
>> On Tue, 26 Jun 2007, Jon Nelson wrote:
>>
>>> On Tue, 26 Jun 2007, Justin Piszcz wrote:
>>>
>>>>
>>>>
>>>> On Tue, 26 Jun 2007, Jon Nelson wrote:
>>>>
>>>>> On Mon, 25 Jun 2007, Justin Piszcz wrote:
>>>>>
>>>>>> Neil has a patch for the bad speed.
>>>>>
>>>>> What does the patch do?
>
> I repeat: what does the patch do (or is this no longer applicable)?
>
>
>>>>> sync_speed_max defaults to 200000 on this box already.
>
> Altering sync_speed_min...
>
>>>>> I tried a binary search of values between the default (1000)
>>>>> and 60000 which resulted in some pretty weird behavior:
>>>>>
>>>>> at values below 26000 the rate (also confirmed via dstat output) stayed
>>>>> low.  2-3MB/s.  At 26000 and up, the value jumped more or less instantly
>>>>> to 70-74MB/s. What makes 26000 special? If I set the value to 20000 why
>>>>> do I still get 2-3MB/s actual?
>
>> Sounds quite strange, what chunk size are you using for your RAID?
>
> The default: 64
>
> md0 : active raid5 sdc4[2] sda4[0] sdb4[1]
>      613409664 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
>
>
> --
> Jon Nelson <jnelson-linux-raid@jamponi.net>
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