Tweak­ing Our Take on SSDs

It’s time to ad­just our aim at an ever-mov­ing tar­get

Maximum PC - - IN THE LAB -

SSDs ARE A PAIN in the ass. At least, they are from a lab-test­ing per­spec­tive. Of all the ma­jor com­po­nents, they’re the trick­si­est to test. For in­stance, it’s sim­ply not vi­able to as­sess long-term per­for­mance of an SSD when you might only be loaned the darned thing for a few days.

Like­wise, the metrics by which SSDs are mea­sured have shifted dra­mat­i­cally over time. At first, it was all about raw band­width. Then it be­came ap­par­ent that drive per­for­mance could de­grade over time. The lat­ter is­sue has been largely re­solved, with well-en­gi­neered drives at any rate. More re­cently, it’s be­come clear that what re­ally mat­ters for desk­top PCs is 4K ran­dom ac­cess at low queue depths.

You can read more about that in our fea­ture on page 36, but suf­fice to say it’s time to tweak our test­ing method­ol­ogy. We were al­ready mea­sur­ing 4K per­for­mance, but now we’re in­creas­ing gran­u­lar­ity by test­ing 4K reads and writes at queue depths of one, two, and four. We’re keep­ing se­quen­tial reads and writes to pro­vide a head­line view of peak per­for­mance.

Like­wise, our 30GB in­ter­nal file copy test re­mains a use­ful real-world test. Ad­mit­tedly, any half-de­cent NVMe drive will chew that bench­mark up, but cheaper SATA drives that lack DDR cache or rely on a small chunk of SLC cache to post de­cent-look­ing se­quen­tial num­bers can be caught out. An ex­am­ple of that is Cru­cial’s new en­trylevel BX500 drive, par­tic­u­larly in 120GB.

That drive can only sus­tain its ad­ver­tised per­for­mance for about 1.5GB of se­quen­tial data, at which point through­put falls off a cliff. Taken to­gether, our tests can’t quite pro­vide that full long-term view of how a drive will stand up to years of use, but the mix of se­quen­tial and ran­dom syn­thet­ics, plus a real-world sense check in the form of our in­ter­nal file copy test, give a good over­all pic­ture of what you can ex­pect.

Cut­ting-edge drives de­mand new metrics.

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