NVME SSDS: EV­ERY­THING YOU NEED TO KNOW ABOUT THIS IN­SANELY FAST STOR­AGE

PCWorld (USA) - - Feature - BY JON L . JA­COB I

NVME (Non-volatile Mem­ory Ex­press) is no longer a nice-to-have stor­age tech­nol­ogy. If you’re shop­ping for a new PC, it’s a fea­ture you should ac­tively seek out. More­over, if your PC is of fairly re­cent vin­tage, you should up­grade to NVME. Here’s why.

NVME is a com­mu­ni­ca­tions stan­dard/ pro­to­col de­vel­oped spe­cially for SSDS by a con­sor­tium of ven­dors in­clud­ing In­tel, Sam­sung, San­disk, Dell, and Sea­gate. It op­er­ates across the PCIE bus (hence the Ex­press in the name), which al­lows the drives to act more like the fast mem­ory that they are, rather than the hard disks they im­i­tate. Bot­tom line: NVME is fast. Re­ally fast. Like never-have-towait-again-for-your-com­puter fast.

NVME: IT’S THE STOR­AGE, STUPID

Not to be­lit­tle the ef­forts of CPU and GPU ven­dors over the last decade, but the rea­son the lat­est top-end PCS seem so much faster is be­cause of the quan­tum leap in stor­age per­for­mance pro­vided by SSDS. Stor­age was the last bot­tle­neck for real and per­ceived per­for­mance, but it’s now wide-pour with a vengeance.

If you’ve bought, say, a Mac­book Pro in the last two years, you may have no­ticed that you hardly wait at all any­more for mun­dane op­er­a­tions. Pro­grams pop open, files load and save in an in­stant, and the ma­chine boots and shuts down in just a few sec­onds.

That’s be­cause the NVME SSD in­side the lat­est Mac­book Pro reads and writes data lit­er­ally four times faster than the SATA SSDS found in pre­vi­ous gen­er­a­tions. Not only that, but it lo­cates them 10 times as fast (seek). That’s on top of the four- to five-fold im­prove­ment in through­put and ten-fold im­prove­ment in seek times al­ready pro­vided by SATA SSDS (over hard drives).

The ap­prox­i­mate per­for­mance ceil­ings for the three main­stream stor­age tech­nolo­gies as things now stand are:

Hard drives still of­fer tremen­dous bang for the buck in terms of ca­pac­ity and are won­der­ful for less-used data. But for your op­er­at­ing sys­tem, pro­grams, and oft-used data, you want an NVME SSD if your sys­tem sup­ports it, or a SATA SSD if it can’t.

SATA SSDS VS. NVME SSDS

There’s a rea­son why we still have SATA SSDS and NVME SSDS. Know­ing the po­ten­tial of mem­ory-based SSDS, it was clear that a new bus and pro­to­col would even­tu­ally be needed. But the first SSDS were rel­a­tively slow, so it proved far more con­ve­nient to use the ex­ist­ing SATA stor­age in­fra­struc­ture.

Though the SATA bus has evolved to 16Gbps as of ver­sion 3.3, nearly all com­mer­cial im­ple­men­ta­tions re­main 6Gbps (roughly 550Mbps af­ter over­head). Even ver­sion 3.3 is far slower than what to­day’s SSD tech­nol­ogy is ca­pa­ble of, es­pe­cially in RAID con­fig­u­ra­tions.

For the next step, it was de­cided to lever­age a much higher-band­width bus tech­nol­ogy that was also al­ready in place—pci Ex­press, or PCIE. PCIE is the un­der­ly­ing data trans­port layer for graph­ics and other add-in cards. As of gen 3.X, it of­fers mul­ti­ple lanes (up to 16 in most PCS) that han­dle darn near 1Gbps each (985Mbps).

PCIE is also the foun­da­tion for the Thun­der­bolt in­ter­face, which is start­ing to pay dividends with ex­ter­nal graph­ics cards for gam­ing, as well as ex­ter­nal NVME stor­age, which is nearly as fast as in­ter­nal NVME. In­tel’s re­fusal to let Thun­der­bolt die ( go.pc­world. com/ltd) was a very good thing, as many users are start­ing to dis­cover.

Of course, PCIE stor­age pre­dates NVME by quite a few years. But pre­vi­ous so­lu­tions were ham­strung by older data trans­fer pro­to­cols such as SATA, SCSI, and AHCI, which were all de­vel­oped when the

hard drive was still the apex of stor­age tech­nol­ogy. NVME re­moves their con­straints by of­fer­ing low-la­tency com­mands, and mul­ti­ple queues—up to 64K of them. The lat­ter is par­tic­u­larly ef­fec­tive be­cause data is writ­ten to SSDS in shot­gun fash­ion, scat­tered about the chips and blocks, rather than con­tigu­ously in cir­cles as on a hard drive.

The NVME stan­dard has con­tin­ued to evolve to the present ver­sion 1.31 with the ad­di­tion of such fea­tures as the abil­ity to use part of your com­puter’s sys­tem mem­ory as a cache. We’ve al­ready seen it with the su­per cheap Toshiba RC100 ( go.pc­world.com/trc) we re­cently re­viewed, which for­goes that on­board DRAM cache that most NVME drives use, but still per­forms well enough to give your sys­tem that NVME kick (for ev­ery­day chores).

WHAT YOU NEED TO GET NVME

It’s pos­si­ble to add an NVME drive to any PC with a PCIE slot via a $25 adapter card. All re­cent ver­sions of the ma­jor op­er­at­ing sys­tems pro­vide driv­ers, and re­gard­less of the age of the sys­tem you will have a very fast drive on your hands. But there’s a catch.

To ben­e­fit fully from an NVME SSD, you must be able to boot the op­er­at­ing sys­tem from it. That re­quires BIOS sup­port. Sigh. Most older main­stream BIOSS do not sup­port boot­ing from NVME and most likely, never will. There’s sim­ply no ben­e­fit to the ven­dors to add it, and a very real down­side: You’re un­likely to up­grade a sys­tem that’s been up­dated with NVME un­less you play PC games or do some­thing truly Cpu-in­ten­sive, like edit­ing 2160p video.

Most NVME SSDS be­ing sold in the

con­sumer space use the M.2 form fac­tor. But sim­ply hav­ing an M.2 slot doesn’t guar­an­tee NVME com­pat­i­bil­ity. M.2 was de­signed to sup­port USB 3.0, SATA, and PCIE. Most early M.2 slots sup­ported only SATA. Read your sys­tem or moth­er­board user’s guide, or check on­line. Note that the MSATA slot, which is the pre­cur­sor, looks very sim­i­lar.

There’s no way to tell from look­ing at a slot whether it sup­ports PCIE and NVME, but you can tell the dif­fer­ence be­tween a PCIE x2 and PCIE x4 slot. The former, called B-keyed (a key is a rise that mar­ries with a gap in the con­tacts on the drive), has six con­tacts sep­a­rated from the rest, while the lat­ter, M-keyed, has five con­tacts sep­a­rated from the rest on the op­po­site side. There is no hard-and-fast rule, but many B-key slots were SATA only. If you have a B/m-keyed slot with both sets of con­tacts sep­a­rated, the most com­mon to­day, you’re golden. These are also some­times re­ferred to as socket 2 and socket 3.

If your socket lets you down, it’s time for the $25 PCIE M.2 adapter card that I men­tioned. Plex­tor’s M9PE and others are avail­able al­ready mounted on PCIE cards as ready-to-rock prod­ucts.

What you as an end-user should avoid are 2.5-inch NVME drives. These re­quire the

SFF-8639 (Small Form Fac­tor) con­nec­tor. An SFF-8639 con­nec­tion fea­tures four Gen 3 PCIE lanes, two SATA ports, plus side­band chan­nels and both 3.3-volt and 12-volt power, but it’s found only in en­ter­prise-level stor­age adapters and sys­tems.

On the off-chance you’re us­ing one of the rare Win­dows PCS that sup­ports Thun­der­bolt (many with Asus moth­er­boards do), you may be able to use an ex­ter­nal Thun­der­bolt PCIE en­clo­sure to add NVME to your sys­tem. This works like a charm on a Thun­der­bolt Mac that’s new enough to run High Sierra.

NOT ALL NVME DRIVES ARE CRE­ATED EQUAL

While just about any NVME should make your sys­tem feel quicker, they are not all alike. Not even close. Where Sam­sung’s 970 Pro ( go. pc­world.com/s970) will read at over 3Gbps and write at over 2.5Gbps, Toshiba’s RC100 ( go.pc­world.com/rc1) reads at 1.2Gbps and writes at just un­der 900Mbps. The dif­fer­ence can be even greater when the amount of data writ­ten ex­ceeds the amount of cache on board.

A num­ber of fac­tors that af­fect per­for­mance, in­clud­ing the con­troller, the amount of NAND on board, the num­ber or PCIE lanes (see above), and the type of NAND. Here are some rules of thumb:

> x4 PCIE NVME SSDS are faster than x2 PCIE types.

> The more NAND chips, the more paths and des­ti­na­tions the con­troller has to dis­trib­ute and store data at. Smaller ca­pac­ity drives are quite of­ten slower than the larger ca­pac­ity drives, even given the same model num­ber.

> The type of NAND used mat­ters. SLC (Sin­gle-level Cell/1-bit) is fastest, MLC (Mul­ti­Level Cell/2-bit) is next, TLC (Triple-level Cell/3bit) is slower, and QLC (Quad-level Cell/4-bit is slowest. How­ever, the for­mula is com­pli­cated by the fact that you can treat any type of NAND (ex­cept SLC) as its faster pre­de­ces­sor by sim­ply writ­ing fewer bits. Ven­dors do this with por­tions of the SSD for use as cache, which means that a TLC or QLC drive can be just as fast as an SLC drive, un­til this cache is used up.

> Most con­trollers these days are very ef­fi­cient, but some, such as those used by In­tel and San­disk, are smarter about how they use cache and can sus­tain write per­for­mance with larger data sets.

Check out our SSD re­views for the skinny on in­di­vid­ual drives ( go.pc­world.com/sr).

NVME MEANS NO RE­GRETS FOR A LONG TIME

If all that hasn’t driven home the point, let’s say it again: NVME is the stor­age tech­nol­ogy you want for your cur­rent or next PC. Un­less you’re a gamer or high-res­o­lu­tion video editor, it vir­tu­ally guar­an­tees that you won’t feel the need to re­place your cur­rent sys­tem for quite a while—at least be­cause of per­for­mance. In­deed, I’ve felt zero com­pul­sion to re­place my six- to seven-year-old sys­tems since they were up­graded with NVME SSDS. Zero.

THE NEW WAVE OF MEMORYBASED STOR­AGE BLOWS AWAY THE OLDER GEN­ER­A­TIONS.

Not that you need sus­tained through­put like this very of­ten, but NVME makes short work of trans­fer­ring files of any size. HDD = 200Mbps, SATA SSD = 550Mbps, NVME SSD = 3Gbps.

The CPU and GPU de­vel­op­ment curve pales in com­par­i­son to that of stor­age over the last 10 years. HD = 2-5 ms seek, SATA SSD = 0.2 ms seek, NVME SSD = 0.02 ms seek. Shorter bars are bet­ter, but this is an over­all av­er­age. Some drives in each cat­e­gory might do bet­ter, some will do worse.

The San­disk Ex­treme Pro of­fers the ex­act same per­for­mance as the WD Black NVME. Be­cause, wait for it—it’s the same drive. The drive uses four PCIE lanes for a the­o­ret­i­cal max­i­mum through­put of well over 3Gbps.

An M.2 NVME SSD such as the rel­a­tively af­ford­able and very fast (ex­cept for ex­tremely large trans­fers) Sam­sung 970 EVO can live in an M.2/PCIE slot, or in a reg­u­lar PCIE slot (x4 or greater) by means of a cheap adapter card.

While our test­bed’s M.2 slot sup­ports PCIE and NVME, yours may not. Shown here is WD’S Black NVME SSD—A very wor­thy drive that sus­tains trans­fers bet­ter than its Sam­sung 970 EVO com­peti­tor.

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