Re: [gentoo-user] RAID 1 vs RAID 0 - Read perfonmance

[Facundo Curti <facu.curti@gmail.com>]

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Thank you all! :) I finally have all clear.
I'm going to do raid 10. Any way, I'm going to do a benchmark before to
install.

Thank you!;)


2014-02-24 14:03 GMT-03:00 Jarry <mr.jarry@gmail.com>:

> On 24-Feb-14 7:27, Facundo Curti wrote:
>
>  n= number of disks
>>
>> reads:
>>    raid1: n*2
>>    raid0: n*2
>>
>> writes:
>>    raid1: n
>>    raid0: n*2
>>
>> But, in real life, the reads from raid 0 doesn't work at all, because if
>> you use "chunk size" from 4k, and you need to read just 2kb (most binary
>> files, txt files, etc..). the read speed should be just of n.
>>
>
> Definitely not true. Very rarely you need to read just one small file.
> Mostly you need many small files (i.e. compilation) or a few big files
> (i.e. database). I do not know what load you expect, but in my case
> raid0 (with SSD) gave me about twice the r/w speed on heavily-loaded
> virtualization platform with many virtual machines. And not only speed
> is higher, but also IOPS are splitted to two disks (nearly doubled).
>
> I did some testing with 2xSSD/512GB in raid1, 2xSSD/256GB in raid0 and
> 3xSSD/256GB in raid5 (I used 840/pro SSD with quite good HW-controller
> but I think with mdadm it might be similar). Raid0 was way ahead of
> other two configurations in my case.
>
> Finally I went for 4xSSD/256GB in raid10 as I needed both speed and
> redundancy...
>
> Jarry
>
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