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From "B. Todd Burruss" <>
Subject Re: Read Latency
Date Tue, 11 May 2010 16:10:15 GMT
you can try this benchmarking tool to compare your drive(s)

... you can simulate various loads, etc.  my RAID0 outperforms single 
drive (as mentioned below) under heavy concurrent reads.

On 05/11/2010 08:15 AM, Peter Schüller wrote:
>> isolated requests, obviously in scale the RAID should perform better... I
>> have not started testing concurrent reads in scale as the single reads are
>> too slow to begin with. I am getting 20-30ms response time off of internal
> Concurrent reads is what you need to do in order to see the benefit of
> a RAID controller with many constituent drives under it.
>> drives and 50-70 ms response time through the raid volumes (as reported in
>> cfstats). The system is totally idle and all data has been cleanly
> That said, a RAID controller imposing several tens of extra
> milliseconds of latency sounds strange; something else or fishy has to
> be going on.
> But don't expect sequential reads of non-cached small random-access
> data to be faster with a RAID controller. The benefit of RAID will
> tend to be overall throughput when doing concurrent reads, fast
> fsync() (low latency on durable writes) and the ability to eat bursts
> of write activity in battery backed cache.

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