Quick Comparison on RAID Levels August 21st, 2013

Vinod Kumar

This blog post is inspired based on tons of customers I meet daily as part of my job. Many customers often ask me which RAID levels to use with SQL Server. Well, the basics and best practices vary between types of files and how the access happens using SQL Server. As a quick recap, data files needs random data access while Log files need sequential access. And then we need tempdb on the fastest drive. All these are general rules of thumb and not something written on stone.

Here is the quick recap of what I suggest based on various dimensions for each of the RAID levels.

RAID Levels

RAID-0

RAID-1

RAID-5 or

RAID-6

RAID-10

Reliability

Lowest

No fault tolerance results in data loss

Very good

Even better with duplexing

Good

Can tolerate single machine fault

Excellent

Storage Efficiency

100%

50%

>50% <100%

50%

Random Read

Excellent

Fair

Worst of the RAID Levels

Fair

Very good

Random Write

Excellent

Fair

Very good

Very good

Sequential Read

Excellent

Very Good

Comparable to a single drive

Good

Generally, better with smaller stripe sizes

Good

Sequential Write

Excellent

Very Good

Better than other RAID levels

Fair

Good

Cost

Lowest

Moderate

Relatively high cost due to redundant drives

Moderate

High

These are important considerations before we build our very own RAID levels as an Administrator. Obviously, the choice always is between RAID-5 or RAID-10. Please use the above table as a quick reference and do let me know if you found more dimensions.

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This entry was posted on Wednesday, August 21st, 2013 at 08:30 and is filed under Technology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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