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posted by martyb on Thursday March 14 2019, @11:58PM   Printer-friendly
from the a-bit-of-an-overstatement? dept.

The Reality of SSD Capacity: No-One Wants Over 16TB Per Drive

One of the expanding elements of the storage business is that the capacity per drive has been ever increasing. Spinning hard-disk drives are approaching 20 TB soon, while solid state storage can vary from 4TB to 16TB or even more, if you're willing to entertain an exotic implementation. Today at the Data Centre World conference in London, I was quite surprised to hear that due to managed risk, we're unlikely to see much demand for drives over 16TB.

Speaking with a few individuals at the show about expanding capacities, storage customers that need high density are starting to discuss maximum drive size requirements based on their implementation needs. One message starting to come through is that storage deployments are looking at managing risk with drive size – sure, a large capacity drive allows for high-density, but in a drive failure of a large drive means a lot of data is going to be lost.

[...] Ultimately the size of the drive and the failure rate leads to element of risks and downtime, and aside from engineering more reliant drives, the other variable for risk management is drive size. 16TB, based on the conversations I've had today, seems to be that inflection point; no-one wants to lose 16TB of data in one go, regardless of how often it is accessed, or how well a storage array has additional failover metrics.

Related: Toshiba Envisions a 100 TB QLC SSD in the "Near Future"
Samsung Announces a 128 TB SSD With QLC NAND


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  • (Score: 3, Insightful) by zeigerpuppy on Friday March 15 2019, @02:58AM (1 child)

    by zeigerpuppy (1298) on Friday March 15 2019, @02:58AM (#814620)

    When we're talking about enterprise storage, larger is not always better. Generally drives are ganged together in groups. More drives generally translates to better performance but higher cost. An array of 8 drives, for instance, may have 2 drive redundancy. Let's say that two drives fail and the controller/software needs to rebuild onto a new drive(s). The rebuild time is then a function of drive write speed x capacity + controller overhead. While the rebuild is happening, the array will be slower (usually controlled by an adaptive algorithm to handle build time vs access speed). A significant issue is that another drive can fail during a rebuild as the array drives need to do a full read of the whole drive, a high load scenario (assuming no write levelling). Therefore, single drive size increases rebuild time and risk of failure during rebuild (which generally means data loss). For 3.5" SAS drives, larger than about 4TB is already risky. For SSDs, it bery much depends on issues like spare blocks and total drive write speed, but 16TB sounds about as big as I'd go with current speeds.

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  • (Score: 2) by legont on Friday March 15 2019, @03:59AM

    by legont (4179) on Friday March 15 2019, @03:59AM (#814655)

    Based on my experience, both consumer at at home and enterprise in the office, reliability picked at 250G spinning drives. Perhaps 500G were almost the same. From that point on it was all downturn.

    --
    "Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.