How to test RAID10 array performance [Debian Wheezy]?
I have created a RAID10 array (near layout) with four 8 GiB virtual hard drives, making a 16 GiB array (/dev/md0 formatted as ext4). On the other hand, I have a 16 GiB RAID1 array (/dev/md1, also formatted as ext4).
The purpose of these setups is to compare the read and write performances of each array.
So far, I have used dd to perform the following tests:
dd (sequential write performance):
Code:
dd if=/dev/zero of=/dev/md0 count=512 bs=1024k
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 6.60623 s, 81.3 MB/s
dd if=/dev/zero of=/dev/md1 count=512 bs=1024k
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 5.74421 s, 93.5 MB/s
dd (sequential read performance):
Code:
dd if=/dev/md0 of=/dev/null bs=4096k
4093+1 records in
4093+1 records out
17168334848 bytes (17 GB) copied, 168.665 s, 102 MB/s
dd if=/dev/md1 of=/dev/null bs=4096k
4093+1 records in
4093+1 records out
17170300928 bytes (17 GB) copied, 44.6421 s, 385 MB/s
So I changed the RAID10 array layout to f2, and sequential read performance improved but the write performance decreased compared to n2 (which was the previous layout):
Code:
dd if=/dev/md0 of=/dev/null bs=4096k
4093+0 records in
4093+0 records out
17167286272 bytes (17 GB) copied, 110.424 s, 155 MB/s
dd if=/dev/zero of=/dev/md0 count=512 bs=1024k
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 6.84386 s, 78.4 MB/s
I was expecting that the RAID10 array would have a better read performance that that of RAID1, but it isn't the case as per these tests - even when I have performed them several times to avoid outliers. I have also used iozone for benchmarking the same setups, with similar results.
I am also aware that other factors may impact performance, such as the hardware used (perhaps virtual hard drives may not provide the best scenario?) and the filesystem.
That being said, what would be the best setup for a RAID10 array that will undergo more reads than writes? (In addition, I am looking for further reasons to use RAID10 instead of RAID1 other than the fault tolerance provided by the latter).
You don't really provide enough information about the actual makeup of the disks, what is the actual backend you are using as this can make a significant difference. How are the devices accessed - there are a shedload more questions on this front.
In general and it is a generalisation the RAID10 (striped then mirrored) should provide the better performance (true also for RAID01) than RAID1. But it is not really possible to comment further than that without knowing a bit more information about your setup.
You don't really provide enough information about the actual makeup of the disks, what is the actual backend you are using as this can make a significant difference. How are the devices accessed - there are a shedload more questions on this front.
In general and it is a generalisation the RAID10 (striped then mirrored) should provide the better performance (true also for RAID01) than RAID1. But it is not really possible to comment further than that without knowing a bit more information about your setup.
Regards
Dave
Dave,
First off, thank you for taking the time to reply to my post. Here are some other details that I hope will be helpful (if there is any other backend information that you need, please let me know):
-Both RAID arrays (1 & 10) were created in the same system.
-uname -a:
Code:
Linux debian 3.2.0-4-486 #1 Debian 3.2.60-1+deb7u3 i686 GNU/Linux
Dave,
Thanks again!
As for pvdisplay and lvdisplay, I must mention here that these RAID arrays are not on LVMs (but here is the output of the commands anyway):
Code:
root@debian:~# pvdisplay
--- Physical volume ---
PV Name /dev/sda5
VG Name debian
PV Size 9.76 GiB / not usable 2.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 2498
Free PE 0
Allocated PE 2498
PV UUID 0VU3Cr-2uLV-68Y8-W9hZ-uwav-APT7-or633a
root@debian:~# lvdisplay
--- Logical volume ---
LV Path /dev/debian/root
LV Name root
VG Name debian
LV UUID Vuyq6i-Ctxr-nz4f-MIYi-x6fB-Fgif-Gjommv
LV Write Access read/write
LV Creation host, time debian, 2014-08-12 21:27:22 -0300
LV Status available
# open 1
LV Size 332.00 MiB
Current LE 83
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:0
--- Logical volume ---
LV Path /dev/debian/usr
LV Name usr
VG Name debian
LV UUID VIKvTb-Kl4V-l2Uw-K5Zp-vjjG-BCoP-MFO2d5
LV Write Access read/write
LV Creation host, time debian, 2014-08-12 21:27:23 -0300
LV Status available
# open 1
LV Size 3.41 GiB
Current LE 874
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:2
--- Logical volume ---
LV Path /dev/debian/var
LV Name var
VG Name debian
LV UUID LPUuFP-JX6Q-ShWJ-otNN-aBvu-DKNg-SxJfcv
LV Write Access read/write
LV Creation host, time debian, 2014-08-12 21:27:23 -0300
LV Status available
# open 1
LV Size 1.66 GiB
Current LE 425
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:3
--- Logical volume ---
LV Path /dev/debian/swap_1
LV Name swap_1
VG Name debian
LV UUID fLMGxe-ksTR-VNbM-rknH-G6OR-Aq1z-Q2RIwP
LV Write Access read/write
LV Creation host, time debian, 2014-08-12 21:27:23 -0300
LV Status available
# open 2
LV Size 560.00 MiB
Current LE 140
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:1
--- Logical volume ---
LV Path /dev/debian/tmp
LV Name tmp
VG Name debian
LV UUID BgKzko-pArn-LGq9-gLRG-xYFM-clc1-dJkzyN
LV Write Access read/write
LV Creation host, time debian, 2014-08-12 21:27:23 -0300
LV Status available
# open 1
LV Size 300.00 MiB
Current LE 75
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:4
--- Logical volume ---
LV Path /dev/debian/home
LV Name home
VG Name debian
LV UUID viKzZn-oOmC-JI88-itWv-26vw-eVoG-6RWWGL
LV Write Access read/write
LV Creation host, time debian, 2014-08-12 21:27:23 -0300
LV Status available
# open 1
LV Size 3.52 GiB
Current LE 901
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:5
root@debian:~#
mdadm.conf (I just realize the definition for /dev/md1 is missing, but I am failing to understand how that would help to the understanding of why the RAID10, with its current configuration, is not performing as well as it should be)
Code:
# Please refer to mdadm.conf(5) for information about this file.
#
# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions containers
# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes
# automatically tag new arrays as belonging to the local system
HOMEHOST <system>
# instruct the monitoring daemon where to send mail alerts
MAILADDR root
# definitions of existing MD arrays
ARRAY /dev/md/0 metadata=1.2 UUID=d9a83766:cdec2926:53d85d4a:01f535ca name=debian:0
# This file was auto-generated on Wed, 10 Sep 2014 23:25:15 -0300
# by mkconf 3.2.5-5
The missing entry in mdadm.conf is a problem - but probably not the cause of your issue. But to eliminate it you should update the file and re-run the test.
You can I think get the correct information by running,
Code:
mdadm --detail /dev/md/1
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How to test RAID10 array performance [Debian Wheezy]?