All-flash arrays: The smart person's guide

All-flash arrays (AFAs) are disrupting the traditional data storage industry. This guide is an entry-level summary of AFA technology.

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Storage-area networks (SAN) and network-attached storage (NAS) are large-scale storage arrays on the inside. The storage array is made of dozens or hundreds of hard disks. What if you replace those hard disks with flash memory? You get an all-flash array (AFA), which is disrupting the traditional data storage industry. This guide is an entry-level summary of AFA technology.

Executive summary

  • What it is: Exceedingly fast! AFAs are entirely solid state. Without any moving parts blocking the bandwidth, your data can travel as fast as wires allow.
  • Why it matters: Speed changes everything. Reducing read/write times tenfold means your entire organization can operate more efficiently — that would please customers and expose any weak links among your partner company's networks.
  • Who this affects: Larger or mission-critical organizations that can afford an all-flash array would see the impact on every department whose users need to access servers.
  • When this is happening: The trend began a few years ago and is still evolving. All of the major storage hardware vendors now offer all-flash (and hybrid disk-flash) arrays, along with specialists — most notably Pure Storage, which became a major player and thus far remains independent.
  • How to get it: You can buy a flash array the same as any other enterprise storage hardware — directly from manufacturers if you're a bigger customer, or through partners/resellers if you are a smaller customer or in a special industry.

What is an AFA?

An AFA is still a SAN or a NAS (or theoretically even a direct-attached file server) — it's the interior drive types that differ, along with system architecture details. Speed is the major advantage. Real-world numbers are hard to determine; generally hard-disk latency is in the low 10s of milliseconds versus low single-digits of milliseconds for flash storage. (There is one real-world example that is easy to see: compare your desktop bootup time with a conventional hard disk, and then install the same operating system on a flash drive. The time saved is astounding.)

Performance can depend on the array's architecture. Some products are traditional arrays retrofitted with flash memory, while others are purpose-built for flash. The latter would be faster. Many storage companies offer both options due to their original market-foothold products (now positioned as hybrids) along with all-flash products that were acquired from startups.

AFA capacity is much lower than that of traditional drive arrays. AFAs currently reach approximate 100 TB, whereas standard drive arrays routinely step into the petabytes of storage. As such, AFAs are best suited for your organization's most speed-sensitive data. They're also best suited for data that needs to be read far more often than written, because each flash drive has a finite (although well-documented) amount of write cycles before it fails.

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Why do AFAs matter?

Speed isn't everything. AFA-based SAN/NAS systems have other advantages versus their spinning-disk counterparts. For example, flash media is physically smaller than hard disks, so the overall rack count can also be smaller. Flash also uses less power, as there aren't any motors to spin or heads to move. This means less heat is produced, which means less cooling is needed, which means less electricity is used, which means more money is saved — after you get over the initial purchasing costs.

Flash drives also have more predictable mean times between failure than regular drives, so replacement budgets are easy to plan. However, if a drive fails unexpectedly, you'd better have a good data backup, because failed flash drives are more difficult to recover than standard hard disks.

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Who does this affect?

AFAs impact any department that relies on networked data storage. Examples are easy to imagine. Engineers could download/upload CAD files in seconds instead of minutes. Customer support staff can answer questions faster and reduce on-hold times by accessing read-centric databases much more quickly. Dynamically produced web pages load faster.

Some applications may need tweaking to efficiently use such fast data storage. That is a reasonable request for custom-built programs, but whether necessary changes will arrive from off-the-shelf applications is a great unknown.

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When is this happening?

This is happening right now, and there is plenty of room for all-flash technology to evolve. The field is still in its mergers-and-acquisitions phase. NetApp recently acquired SolidFire for $870 million. Kaminario and Violin Memory are important independent players, according to market research firm International Data Corp.

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How do I get it?

Generally, purchasing an AFA costs more than a traditional hard-disk-filled SAN or NAS on a per-terabyte basis, simply because flash memory costs more than spinning media. However, customers feel that AFAs are easier to install and maintain than the alternatives. EMC (soon to be Dell), IBM, Hitachi, HP Enterprise, NetApp, Oracle, and Pure Storage are the major players.

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