Around the middle of 2012, there was only one standard version of AWS’ EBS cloud storage volumes, the EBS standard volume. This volume offered persistent data for EC2 instances and is now known as the Magnetic volume. Over the last year and half, AWS has announced two more volume types in order to meet the growing demands of performance and lower costs. The three types that are now available include Magnetic, Provisioned IOPS (SSD) and General Purpose (SSD) EBS volumes. All three have their merits and offer similar functionalities, such as snapshot capabilities, though they differ largely in cost and performance.
In contrary to the past one standard volume, today AWS users need to select the right kind of volume based on requirements such as, cost effectiveness or performance. In this article, we will provide an overview of all three volume types and insights on their cost and performance.
Volume I: Magnetic EBS Volumes
While magnetic hard disks are seemingly of an older generation, they are still found in the majority of machines in the tech world today due to their cost effectiveness. However, it seems like Magnentic volumes are on their way out seeing as they are not ideal for critical production applications. This theory is strengthened by two points. Firstly, whenever a user tries to launch a new instance with a magnetic root device, AWS prompts the user to switch to the new SSD model. Secondly, Magnetic volumes will not support the newer 16 terabyte EBS volumes, which suggests that AWS’ intention is to remove the Magnetic volume altogether.
The primary disadvantage of Magnetic EBS volumes is their performance in comparison to their price. They offer 100 IOPS that can burst to a few hundred IOPS, however, 100 IOPS is considerably lower than that of the IOPS offered by other options. Furthermore, while Magnetic EBS volumes are undeniably cheaper, at $0.05 per GB/month (in the US-East region, as of January 2015), than the other available volumes, the money saved may be an illusion. You pay an additional cost per I/O with Magnetic EBS volumes, as well as the cost of the service. This may reach a high cost per month, particularly if implemented in a busy production environment.
A Magentic volume’s performance can be improved by striping multiple volumes together. It can be a good fit for low IOPS and disk size requirements, such as where data is accessed less frequently.
Volume II: General Purpose SSD EBS Volumes
Unlike their predecessor, at only a few months old, General Purpose (GP) EBS volumes are ideally suited for busy production environments, seeing as they offer the best cost-performance ratio. This volume type is the new default disk type, and with good reason. While the cost is double than that of Magnetic volumes, with GP you are not obligated to pay for I/Os beyond the initial price. Therefore, if you need frequent access to data, GP volumes are the right choice since they ultimately result in lower costs.
The performance speed of 1TB GP EBS volumes can burst up to 3,000 IOPS per second. This, of course, is no match for the meager 100 average outlined in the Magnetic EBS statistics, so this volume type boasts far more than just cost efficiency. All in all, GP EBS volumes are rapidly establishing themselves as the leading EBS type available in the AWS cloud.
This volume offers 3 steady IOPS per GB of storage and works on I/O credits. Larger volumes may accumulate a higher credit, which can help burst beyond the 3 IOPS per GB standard.
Volume III: Provisioned IOPS Volumes
The third and final volume type is the PIOPS EBS model. Another “youngster” in the EBS world, PIOPS is even faster than GP volumes, reaching up to 4,000 IOPS per second for a 1TB volume. While on the surface this sounds ideal, the improved performance comes at a high cost. At $1.25/GB/month and an additional $.065/provisioned IOPS (in the US-East region, as of January 2015), it is considerably more expensive than both of the other models. While the higher speed is a very nice perk, it does not always warrant the additional cost, and AWS users must carefully consider the need for high performance over reduced cost efficiency.
It is also important to note that PIOPS offers almost 90% of the provisioned IOPS during the life of an EBS volume, whereas GP offers 3 steady IOPS per GB and burstable performance based on I/O credit. Thus, PIOPS can be useful when users need very high and consistent I/O.
Using the Magnetic model is only recommended in a relatively static production environment. GP volumes surpass both the cost efficiency and performance of their predecessor, particularly in cases of frequent data access. As the leading EBS volume available today, GP is only outshined by the PIOPS in terms of performance speed. This performance, however, is only necessary in cases where heavy I/O loads prove to be too much for the 3,000 IOPS in the GP model, a situation that does not present itself very often. In this case, however, it is important to identify your real I/O requirement. A possible tool to help find an application’s I/O is IOStat, a tool available with Linux that summarizes your I/O usage. On the other end of the spectrum, Perfmon, which is an integral part of Windows, creates a log on the physical disk, documenting the number of I/Os per second. Knowing these facts is important when selecting the EBS volume type that best suits your needs.
|Magnetic||$.05/GB/month + $.05/million I/O||Up to 100 IOPS/volume||Only useful for little to no data access.|
|GP||$.10/GB/month||Up to 3000 IOPS/volume||Very useful for the majority of users, specifically for larger volumes needs.|
|PIOPS||$0.125/GB/month + $.065/provisioned IOPS||Up to 4000 IOPS/volume||Most useful for users needing high speed.|
Let’s assume that an application needs 1,000 IOPS with 500GB of minimum storage. If we compare the cost of all three volumes types:
- Magentic: By only offering 100 IOPS, users would have to stripe 10 50GB volumes together. This may not be an ideal situation for snapshots and HA, but the cost comes out to:
Storage Cost: 500 * 0.05 = $25/month
I/O Cost : 100 IOPS/volume = $13/volume * 10 volumes = $130
Total Cost: $155/month with 1,000 IOPS
* This calculation assumes that the Magnetic volume was utilized to its fullest extent (100 IOPS at all times). In practice, this level of throughput may only be required in bursts, so the total number of I/O operations would most likely be lower, resulting in a lower cost, as well.
- Provisioned IOPS: By provisioning 1,000 dedicated IOPS almost 90% of the time, the cost comes out to:
Storage Cost: 500 * 0.125 = $62.5
IOPS Cost : $65
Total Cost: $127.5/month with 1,000 IOPS
- General Purpose Volume: This volume offers 3 IOPS/GB, which translates into 1,500 IOPS and a cost of:
Storage Cost: 500*0.10 = $50
Total Cost: $50/month with 1,500 IOPS
The numbers show that when you need larger storage and more IOPS, general purpose (GP) would be the best possible option in terms of the cost-performance ratio.
Once again, it is very important to note that all three volume types support durable snapshot capabilities. This considerably eases the pressure of choosing an appropriate EBS type, since snapshots can be used with all of them. N2Ws’ CPM protects all three types of EBS volumes, making it possible for you to maintain your snapshots at all times. So regardless of which EBS volume type you choose, it is important to relax and remember that no decision is irreversible.