Gentoo Archives: gentoo-user

From: Facundo Curti <facu.curti@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] RAID 1 vs RAID 0 - Read perfonmance
Date: Mon, 24 Feb 2014 18:50:23
Message-Id: CABxff5_b+GcREraznf_6-XWqe8284TFTUnagZZ087pQ0sc4XZQ@mail.gmail.com
In Reply to: Re: [gentoo-user] RAID 1 vs RAID 0 - Read perfonmance by Jarry
1 Thank you all! :) I finally have all clear.
2 I'm going to do raid 10. Any way, I'm going to do a benchmark before to
3 install.
4
5 Thank you!;)
6
7
8 2014-02-24 14:03 GMT-03:00 Jarry <mr.jarry@×××××.com>:
9
10 > On 24-Feb-14 7:27, Facundo Curti wrote:
11 >
12 > n= number of disks
13 >>
14 >> reads:
15 >> raid1: n*2
16 >> raid0: n*2
17 >>
18 >> writes:
19 >> raid1: n
20 >> raid0: n*2
21 >>
22 >> But, in real life, the reads from raid 0 doesn't work at all, because if
23 >> you use "chunk size" from 4k, and you need to read just 2kb (most binary
24 >> files, txt files, etc..). the read speed should be just of n.
25 >>
26 >
27 > Definitely not true. Very rarely you need to read just one small file.
28 > Mostly you need many small files (i.e. compilation) or a few big files
29 > (i.e. database). I do not know what load you expect, but in my case
30 > raid0 (with SSD) gave me about twice the r/w speed on heavily-loaded
31 > virtualization platform with many virtual machines. And not only speed
32 > is higher, but also IOPS are splitted to two disks (nearly doubled).
33 >
34 > I did some testing with 2xSSD/512GB in raid1, 2xSSD/256GB in raid0 and
35 > 3xSSD/256GB in raid5 (I used 840/pro SSD with quite good HW-controller
36 > but I think with mdadm it might be similar). Raid0 was way ahead of
37 > other two configurations in my case.
38 >
39 > Finally I went for 4xSSD/256GB in raid10 as I needed both speed and
40 > redundancy...
41 >
42 > Jarry
43 >
44 > --
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49 >