Comparing RAID 1 and RAID 5
Using RAID 1 or 5 has become much more affordable over the years when it comes to redundancy on servers. Both hardware RAID 1 (mirroring or duplexing) or RAID 5 (striping with parity) offer good data redundancy should a single hard drive in a RAID array fail. The major difference however can be found in the system performance between RAID 1 and RAID 5. RAID 5 experiences more heavy write overhead because of the additional parity data that has to be created and is then written to the disk array. RAID 1 does not experience this overhead.
Read performance, on the other hand, is usually better with a RAID 5 setup. This gets even better if your RAID 5 array has more than 3 disk. RAID 5 read performance increases with more disks in an array because the more disks there are, the more read/write heads there are, and RAID 5 arrays have the awesome ability to read simultaneously from all the drives at the same time. RAID 1 only has two disk drives by nature and is therefore limited in the number of read/write heads.
Drilling further down into this subject a server setup should be thoroughly investigated to decide which option to choose. If your server supports enough drives, a popular setup is a RAID 1 setup for the OS (Operating System) and a RAID 5 setup for the data. There are certain applications like SQL databases that eventually work better in a different setup, but for most standard setups the described option works fine.
In the web hosting world a good approach would be a setup with RAID 1 and a standalone hard drive for the backups. This gives the web host protection from a single drive failure while it is less an issue if the hard drive for backups fails. In my case I use an external backup service and rsync my backups from the backup standalone hard drives to the external location. If the stand-alone hard drive fails I just re-populate it from the external source and all is good. Another advantage for putting the backups on a different is system performance. While the web server is hosting customer websites and is busy serving pages the stand-alone disk is used for writing the backups to it while the read process is on the RAID-1 array.
For a dedicated server hosting large databases a different approach can make more sense. Let’s assume you would be hosting a large SQL Server database. A server setup could look like this.
System/OS = RAID 1
Database = RAID 5
Database Logs = RAID 1
Not every server can hold that many drives, but it really depends on your budget anyway. The listed configuration is made for best performance. First of all we separate the operating system from the application. The database itself has a lot of read processes to take care of and RAID 5 provides best performance. The database logs are written to before they get truncated. So, using RAID 1 here provides better peformance.
Conclusion: When building your next web server do some research on what the server will do. With the knowledge from this article you might be able to gain some better performance from the system. And if you go with a standard volume/RAID 0 setup that is fine, too. As long as you are aware that there is no redundancy and you have a proper Disaster Recovery plan in place that suits your needs … go for it.
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