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Part 4 of a 5-part series on choosing media for NetApp FAS storage


By Tushar Routh, Sr. Manager, Storage Products, NetApp

 

storage-subsystem-design.pngIn this post I’ll talk about how to take the components I discussed in the previous posts in this series—HDD, SSD, and shelves and interconnects—and put them together into a storage subsystem that will meet your needs now and in the future.

 

FAS Storage Guidelines

With all the recent attention to flash storage, it would be easy to conclude that HDDs are going to be eclipsed in short order. There are certainly use cases for dedicated all flash arrays, which is why NetApp released the EF540 Flash Array last year, and why we’re busily working on FlashRay, our next generation, scale-out all-flash offering.

 

However, HDDs—especially in combination with flash—aren’t going away any time soon. The economics of HDD and HDD/flash solutions relative to all-flash still make them the sweet spot for a lot of storage workloads.

 

Here’s what NetApp suggests:

 

  • For applications that need the most consistent performance with the lowest latency, choose the EF540 Flash Array or a FAS system with SSDs.
  • For other high-end workloads, deploy FAS with performance disks in combination with one (or more) of our flash-based caching technologies: Flash Cache (storage controller level), Flash Pool (disk subsystem) or Flash Accel (server caching). NetApp put a lot of time and effort into providing options to let you put flash where you need it. (You can find more guidance on choosing among flash options in our recently released Flash Storage for Dummies guide, this Tech OnTap article, and this white paper.)

    The DS2246 disk shelf is the best choice for this type of deployment because it can accommodate performance HDDs, SSDs, or a combination (for Flash Pool deployments) and because it offers superior performance density.
  • For nearline or capacity-oriented workloads, deploy capacity disks in combination with flash. The DS4246 disk shelf is a good choice here because it supports both high-capacity HDDs and combinations of HDDs and SSDs.
  • For backup or archival workloads, deploy capacity disks. The DS4486 disk shelf delivers maximum capacity per rack unit.
  • For purely sequential workloads, capacity or performance disks deliver good performance at a lower price than SSDs.
  • If you’re not sure what the I/O characteristics of your workload are, or you need to support a variety of workloads that may include both transactional and sequential I/O patterns, HDD plus flash options are once again a good bet.

 

disk-shelves-link.pngBest Practices

Here are a few best practices to keep in mind. 

 

  • Except for Flash Pool, don’t mix different media types in the same SAS stack.
  • A single FAS system can support multiple aggregates with different media types (performance HDD, high-capacity HDD, SSD) to address the needs of different workloads, or you can deploy clustered Data ONTAP and dedicate specific cluster nodes for specific media and workload types.
  • Use RAID-DP (with the possible exception of SSDs deployed for Flash Pool).
  • Make sure RAID scrubs are turned on for RAID groups containing HDDs (this is the default setting) to keep your drives healthy.
  • When deploying storage where length limitations are likely to be an issue, or when deploying a “stretch” MetroCluster, choose optical SAS for easier cabling. (Optical SAS will be available later this month.)
  • Follow the guidelines in the recently updated Storage Subsystem Resiliency Guide [9] to achieve maximum resiliency.

 

Wrap Up

 

A little up front planning—and consideration of the guidelines I’ve outlined here and in previous posts—will go a long way in helping you choose storage that is best suited for your particular workloads and needs. As you’ve no doubt noticed, there are a lot of options to consider: HDD versus SSD, SSD deployed as cache or persistent storage, different capacity points, and so on. Of course, NetApp experts as well as our worldwide network of partners are available to assist you in your decision-making.

 

You may have also noticed that I haven’t said anything about security up to this point. In the final blog post, I’ll wrap up this series with a discussion of NetApp Storage Encryption.

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