Guide to choosing raid type on VMware ESX for beginners

Posted by on March 9, 2010 in VMware | 2 comments

For newer admins or those without a storage background, this is a common question that I hear often. What type of RAID should I use for my data stores to host Virtual Machines. This is not meant to be a high level storage best practice document. I’m just covering some basic details that should help new admins and SMB customers.

First thing you need to do is do some research on what type of servers you will be Virtualizing and what their IO needs might be. The main reasons for choosing different RAID levels will be performance and redundancy. Most people tend to lean towards RAID 5 which provides good performance with a high level of redundancy. See the chart below for some more details. You can also review some details from VMware here.

Summary of the different RAID types

Type RAID 0 RAID 1 RAID 1+0 RAID 5
Method Striping Mirroring Mirror and striping Stripe with Parity
Description The data is striped across all the disks in the set. Not true RAID because it is not redundant. Exact copies of the data are kept across paired disks or disk sets. A striped array whose segments are a mirror set. Not to be confused with 0+1 The data is striped across all the disks in the RAID set, along with the parity information needed to reconstruct the data in case of disk failure.
Performance Good. All IO is spread and no parity overhead Twice the read rate but writes occur twice Combines speed efficiency of the RAID 0 (stripe set) with a fault tolerance of RAID 1 (mirror). High read and medium write performance. A good balance of performance and availability.
Typical use Data you can afford to loose, such a pre-production, image/video editing. Data requiring high availability, such as accounting or payroll. Transactional type data such as database logs. File and application servers. Typically everything that does not have a specific requirement.
Parity Calculation None None None Yes
Redundancy None Yes Yes Yes
Minimum Disks 2 2 4 3
Storage Overhead 0% 100% 100% Capacity of one disk in the set. 33% for a 3 disk set.

About Brian Suhr

Brian is a VCDX5-DCV and a Sr. Tech Marketing Engineer at Nutanix and owner of this website. He is active in the VMware community and helps lead the Chicago VMUG group. Specializing in VDI and Cloud project designs. Awarded VMware vExpert status 6 years for 2016 - 2011. VCP3, VCP5, VCP5-Iaas, VCP-Cloud, VCAP-DTD, VCAP5-DCD, VCAP5-DCA, VCA-DT, VCP5-DT, Cisco UCS Design


  1. Brian
    Nice Summary

    Do you have any experience with the configuration of the strip sizes for the RAID sets ?

    A starter guide for newbies on aligning the stripe size / Cluster / Bloc size int the various environments seems impossible to find.

    I’ll be happy to contribute as I have an interest ?

    • Hey Sean, Its not something that I do much of. I would typically work with one of our storage focused architects when I need something like this. If you have interest in putting something like this together and do not have a place to publish, I am open to you doing a guest post here if thats of interest.

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