Amazon EBS RAID Considerations

 

Each EBS volume attached to an instance is constituted on independent storage hardware within the AWS infrastructure. SoftNAS Cloud® storage pools should therefore be configured as RAID 0 to stripe across multiple EBS volumes to gain the highest possible bandwidth and performance. Using any RAID level beyond RAID 0 (RAID levels 1, 10, 5, 6, and 7)  merely increases storage costs with little to no benefit to reducing failure rate or improving performance.

 

EBS General Purpose SSD are limited to 10,000 IOPs per volume.  EBS Provisioned IOPs are limited to 20,000 IOPs per volume.  EBS Magnetic are more severely limited to 40-200 IOPs, which represents the maximum capabilities of today’s spinning media.  In testing we have seen the EBS SSDs provide more IOPs in shorter durations, but sustained IOPS usage shows these to be bursts that are forced into alignment with disk limitations. By striping across multiple EBS Volumes, of any type, the IOPs can be higher than a single EBS Volume can provide.

 

AWS EBS annual failure rate (AFR) is published to be between 0.1% and 0.2%.  Aggregating multiple EBS volumes within a SoftNAS Cloud® storage pool will magnify the AFR.  The AFR is roughly the number of EBS volumes multiplied by AFR rate.  Our recommendation is to understand the risk and size of (number of volumes within) storage pools appropriately.  Using five EBS  volumes within a storage pool (totaling up to 80 TB of capacity) will be an acceptable AFR for most use cases, and many use cases can tolerate an even higher AFR.

For high capacity deployments, use multiple SoftNAS storage pools. By setting EBS volumes into separate storage pools, you can achieve high performance and capacity, without adversely affecting AFR.