SSDs – Write Endurance Myths

I happened to be reading a comment on another website the other day where the commenter claimed SSDs would never be viable alternatives to traditional magnetic hard drives until manufacturers solved the “100,000 rewrite cycle issue.” StorageSearch.com’s SSD Myths and Legends – “write endurance” attempts to put this claim to bed once and for all.

The main point is that most of the SSD drives being sold today have write endurances ratings in the 1 to 5 million rewrite cycle range. The 100,000 limit was the maximum available in the late 1990s, but has long since been superseded.

The upshot of this is that even using extremely data intensive applications that write and rewrite large amounts of data over and over again to and SSD, the user is looking at decades of such intensive use of an SSD before it fails.

This is why typically, SSDs released today have MTBF ratings equivalent to those of magnetic hard drives (not that there aren’t issue with MTBF as a guide to hard drive reliability, but rather that there is nothing about recent SSDs that will make them fail more frequently than their magnetic bretheren).

2 thoughts on “SSDs – Write Endurance Myths”

  1. I was always told that you will never see a problem with the NAND reaching its write limits but the control itself is the problem with SSDs. If this is the case then as later generations come out the better write strength will become.
    Intel in my opinion is going down this route where Sandforce is going for speed over reliability. To give you a idea (based off specs alone atm) a Intel x25-m G2 will last
    Total 4KB Random Writes (Drive Lifespan)
    G2 x25-m 7.5TB – 15TB
    G3 x25-m 30TB – 60TB

    Considering there is twice as much per NAND chip between the 34nm and 25nm size (thus 50% cheaper to produce) its strengthens my belief that the controller is the problem with writes and not the NAND.

    So long as you do the basics and lower how much your OS/Browser writes to your SSD you should be just fine.

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  2. Remember to distinguish between the different memory technologies used in Flash drives when evaluating the write endurance.
    Per Wikipedia:

    The write endurance of SLC floating-gate NOR flash is typically equal or greater than that of NAND flash, while MLC NOR and NAND flash have similar endurance capabilities. Example Endurance cycle ratings listed in datasheets for NAND and NOR flash are provided.

    SLC NAND flash is typically rated at about 100k cycles (Samsung OneNAND KFW4G16Q2M)
    MLC NAND flash is typically rated at about 5–10k cycles (Samsung K9G8G08U0M)
    SLC floating-gate NOR flash has typical endurance rating of 100k to 1M cycles (Numonyx M58BW 100k; Spansion S29CD016J 1,000k)
    MLC floating-gate NOR flash has typical endurance rating of 100k cycles (Numonyx J3 flash)

    Since manufacturers have moved to MLC technology in order to increase storage capacities, the actual endurance ratings are back in the 100k range.

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