Hardware RAID vs Software RAID

On the recent few server launches, we have acquired one of the latest hardware RAID card from LSI (LSI 3ware SAS9750-4i). So, it's time for a test.

Server specs:-
1 x Intel Xeon 5504
4GB DDR3 ECC RAM

RAID hardware: LSI 3ware SAS9750-4i
Configuration: RAID5
Hard Disk: 3 x 500GB WD RE3

[root@localhost ~]# dd if=/dev/zero of=test.img count=300 bs=10M

300+0 records in

300+0 records out

3145728000 bytes (3.1 GB) copied, 106.22 s, 29.6 MB/s (writing speed)

[root@localhost ~]# dd if=test.img of=/dev/null bs=10M

300+0 records in

300+0 records out

3145728000 bytes (3.1 GB) copied, 1.18725 s, 2.6 GB/s (reading speed)

And it's time to test the rebuild speed. HOT pull out one of the Hard Disk and insert it back to rebuild. The rebuilding time was about 2hrs for 500GB drive

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RAID hardware: None, mdadm
Configuration: RAID1
Hard Disk: 2 x 500GB WD RE3

[test@localhost ~]$ dd if=/dev/zero of=test.img count=300 bs=10M

300+0 records in

300+0 records out

3145728000 bytes (3.1 GB) copied, 30.1198 s, 104 MB/s (writing speed)

[test@localhost ~]$ dd if=test.img of=/dev/null bs=10M

300+0 records in

300+0 records out

3145728000 bytes (3.1 GB) copied, 10.175 s, 309 MB/s (reading speed)

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RAID hardware: None, mdadm
Configuration: RAID0
Hard Disk: 2 x 500GB WD RE3

[user@localhost ~]$ dd if=/dev/zero of=test.img count=300 bs=10M

300+0 records in

300+0 records out

3145728000 bytes (3.1 GB) copied, 13.5305 s, 232 MB/s (writing speed)

[user@localhost ~]$ dd if=test.img of=/dev/null bs=10M

300+0 records in

300+0 records out

3145728000 bytes (3.1 GB) copied, 1.0086 s, 3.1 GB/s (reading speed)

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Comparison:

From the result, it show that RAID 0 has the best performance but the trade off is the reliability as it has a single point of failure comparing with RAID1 and RAID5.

Write performance is poor on RAID 5 due to the parity bit calculation and this setup is not recommended to host application which require intensive write operations. If you need good read and write performance with redundancy, consider RAID 10.

RAID1 is my favorite setup as it has the balance on all factors (space, reliability, performance) due to its simplicity, reliability and performance. RAID1 setup is recommended for simple and basic server setup.