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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