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A Look at Cloud Storage Component Technologies Trends and Future Projections

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Data in the cloud are stored in isolated regions or bits on media in storage components (i.e., in magnetic bits on tape media in Linear Tape Open (LTO) cartridges, in magnetic bits on disk platters in HDD, or in electric charge levels on silicon-based flash memory (NAND) chips). The landscape associated with technologies that produce tape, HDD and NAND components includes both economic metrics (i.e., component revenue and bit shipments) as well as technology metrics, (i.e., bit densities and cost per bit and manufacturing trends).

Storage decisions by cloud providers depend critically on future trends in storage technology. Such decisions rely on an assumption of Moore’s Law progress—that an increasing figure of merit grows by a factor (1 + α)n where n is the number of years, α x 100 is the annual percentage increase and that a decreasing figure of merit reduces by a factor (1 - β)n where n is the number of years, β x 100 is the annual percentage decrease. Ideal Moore’s Law progress has α = 0.4 (e.g., bit density doubles every two years) and β = 0.3 (e.g., cost/bit halving every two years). The last nine years of storage landscape history presented in this paper show that storage technologies aren’t achieving ideal Moore’s Law metrics.

Nine-Year Storage Landscape History

Table 1 lists technology and economic trends over the last nine years for three storage media classes: NAND Flash, HDD and LTO Tape Media. The selected trends include units shipped (or wafers processed) to measure manufacturing capacity, Petabyte (PB) shipments, areal density (bits/in2), revenue and cost per gigabyte ($/GB).

Data for Table 1 are obtained from publically available sources: LTO Tape Media data from the LTO Consortium and Santa Clara Consulting Group (SCCG), HDD data from Quarterly Report Statements for U.S.-based HDD manufacturers, NAND Chip data from DRAMeXchange Quarterly Revenue Reports5 and investor presentations from NAND chip manufacturers. Since HDD data is not publically available from non-U.S. manufacturers, total available market (TAM) data from U.S. manufacturers for hard disk drive units showing non-U.S. manufacturers TAM at 15 percent is used to scale final HDD revenue and PB shipments data in Table 1.

Cost per bit data represents a value averaged over all products (i.e., total component revenue in a year divided by total bits shipped in that year). Areal density refers to the maximum areal density in any product recognizing that most technologies offer an array of products using different areal densities. Tape media data is limited to the LTO product space since only these data, and not enterprise tape product data, are publically available. NAND data is for manufactured dies (e.g., chips) and excludes SSD that use these NAND components. Similarly, LTO Tape Media data is for cartridges only and excludes tape drives and library robotics. Finally there is a discontinuity in the LTO Tape Media data for $/GB between 2014 and 2015 related to SCCG no longer reporting $/GB for LTO media and the LTO Consortium only reporting cartridge units and bit shipments. $/GB for LTO Media for 2015 and 2016 were calculated using publically available year-end cartridge costs.

Three observations follow from Table 1:

  1. In 2016, HDD technology dominated manufactured storage by accounting for 81 percent of bit shipments versus 14 percent for NAND and 5 percent for LTO Tape Media making the prospect of NAND storage replacing HDD storage in the near term horizon unlikely, even though the HDD storage share of manufactured bits is decreasing from 2013 values (see Figure 1)
  2. Total manufactured exabytes (EB) of storage, 1000 PB = 1 EB, exhibits a linear trend rather than a geometric trend (see Figure 2)
  3. Total storage component revenue appears to be plateauing rather than increasing with a shift in revenue from HDD to NAND components (see Figure 3)

Table 2 recasts the storage landscape data in Table 1 by examining annual change trends over the last nine, three and one years to better compare the growth of storage metrics relative to ideal Moore’s Law performance. Areal density trends show no technology achieving the ideal 40 percent Moore’s Law metric for areal density, the driver for increased component capacity. NAND aided by lithography for fabricating smaller features and a migration from 2 bit per cell to 3 bit per cell structures has realized 33 percent annual increases in areal density. Note that two-year product cycles for LTO TAPE distort its one-year areal density trend since the next LTO tape product will be introduced this year, producing an appropriate density trend line closer to 25 percent. HDD areal density increases lag by a factor of ~2 both the NAND and TAPE values. $/GB trends for NAND, HDD and LTO tape media show annual decreases in the 20 percent range rather than the perceived Moore’s Law metric of 30 percent.

Bit shipment growth shows the strong performance of NAND, essentially doubling bit production (45 percent per year) every two years. This growth is attributed to consumer-based demand in personal appliances, emerging cloud storage demands, annual 6 percent increases in wafer capacity and annual areal density increases of 33 percent. Both LTO Tape and HDD bit shipments have sustained 20 percent annual growth over the last nine years. Revenue growth for HDD and LTO Tape media show decreasing nine-year trend lines (-3 to -5 percent) in contrast to stable 18 percent annual growth in NAND over the same period. The major differentiator for these technologies remains cost per bit, which in 2016 were $0.320/GB for NAND, $0.039/GB for HDD and $0.0162/GB for LTO Tape Media.

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