What drives your mu­sic?

Un­der­stand­ing Hard Disk and Solid State Tech­nolo­gies and How They Re­late To Mu­sic Stor­age

NOVO - - CES2013 - Mal­colm J. Gomes

Over the past few years, one of the big­gest changes in the audiophile world is that com­puter au­dio has be­come main­stream. Ev­i­dence of this can be found at all the ma­jor au­dio shows from TAVES to CES to RMAF to name a few. I was sur­prised to see so many ex­hibitors at re­cent au­dio shows, demon­strate their equip­ment us­ing a lap­top and a DAC as their source com­po­nents, some­times even to the ex­clu­sion of the ven­er­a­ble turntable. It is sad to see the once ubiq­ui­tous CD player be­ing slowly but surely sup­planted.

This trend has put the spot­light on ex­ter­nal drives that store the mu­sic and thanks to tech­no­log­i­cal ad­vances and economies of scale, this cat­e­gory of prod­ucts has seen sizes and prices con­tinue shrink to a level where they have be­come in­cred­i­bly af­ford­able. Cur­rently, the most pop­u­lar type of drive is un­doubt­edly the Hard Disk Drive or HDD be­cause they of­fer the best bang for your buck in terms of stor­age ca­pac­ity and price com­pet­i­tive­ness. To­day, many brands of­fer 1 to 3 ter­abyte HDDs for around $100 to $300.

HDDs come in dif­fer­ent sizes and shapes, which are de­ter­mined, by the size and shape of the com­po­nents that are uti­lized to pro­duce the de­vice. The con­ven­tional HDD is built around a plat­ter or op­ti­cal disc with a spin­dle mo­tor mak­ing it ro­tate at the re­quired speed.

Solid State Drives and a Lit­tle His­tory

Look­ing to the fu­ture, many pun­dits are fore­cast­ing that the HDD will soon face stiff com­pe­ti­tion from the more durable Solid State Drive or SSD, which has al­ready started mak­ing some mean­ing­ful in­roads into the mar­ket. Many peo­ple re­gard the SSD as a new devel­op­ment that has re­cently emerged in the con­sumer sphere. How­ever the sur­pris­ing fact of the mat­ter is that SSD tech­nol­ogy is more than half a cen­tury old.

The ge­n­e­sis of SSDs can be traced to the 1950s when two tech­nolo­gies namely ‘core me­mory’ and ‘card ca­pac­i­tor read only source’ com­monly re­ferred to as

aux­il­iary me­mory units emerged dur­ing the age of vac­uum tube com­put­ers. They were soon sup­planted by drum stor­age type drives, which were a lot cheaper to man­u­fac­ture. Then dur­ing the 1970s we saw the de­but of drives im­ple­mented in semi­con­duc­tor me­mory of the su­per­com­put­ers of the day in­clud­ing names like Cray, IBM and Amd­hal. At the time th­ese were built to or­der and car­ried as­tro­nom­i­cal prices, which kept them out of the con­sumer sphere.

Things changed in 1978 when Texas Me­mory Sys­tems devel­oped a 16 kilo­byte RAM solid-state drive, which be­came the dar­ling of oil com­pa­nies as it helped them in seis­mic date ac­qui­si­tion. The very next year Stor­ageTek de­signed a new kind of solid-state drive and a few years later the PC-5000 was un­veiled by Sharp. This caused quite a buzz be­cause of its 128 kilo­byte solid-state stor­age car­tridge which in­cor­po­rated bub­ble me­mory. At the time this was con­sid­ered as very high stor­age ca­pac­ity for an SSD.

In 1986, Santa Clara Sys­tems launched its Ba­tRam 4 megabyte stor­age sys­tem that could be ex­panded to 20 megabytes us­ing add-on mod­ules. Around a decade later M-Sys­tems devel­oped a ash based solid-state drive that could with­stand ex­treme shock, tem­per­a­tures and vi­bra­tion and had a much longer mean time be­tween fail­ure (MTBF) rate. This made them great for mil­i­tary and aero­space ap­pli­ca­tions. In 2006 Sandisk ac­quired MSys­tems and went on to be­come one of the ma­jor play­ers in this seg­ment.

Hard Disk Drive Ver­sus Solid State Drive

The big­gest dif­fer­ence be­tween HDD and SSD is that the former are electro­mechan­i­cal de­vices that in­cor­po­rate spin­ning discs and mov­able read and write heads, while the lat­ter uses mi­crochips and to­tally elim­i­nates the need for mov­ing parts. This means that SSD me­mory is less sus­cep­ti­ble to phys­i­cal shock, op­er­ates qui­etly and of­fers lower ac­cess time and la­tency. The tran­si­tion form HDDs to SSDs should be quite smooth be­cause of the fact that they both use the same in­ter­face (con­nec­tor type) and so switch­ing from one to the other does not present any com­pat­i­bil­ity prob­lems at the con­sumer level.

Types of Solid State Drives

When choos­ing an SSD it would be­hove you to opt for one that has ash me­mory as th­ese have the abil­ity to re­tain me­mory even with­out power. If your ap­pli­ca­tion re­quires a higher in­put/out­put rate and bet­ter re­li­a­bil­ity you could con­sider en- ter­prise ash drives (EFDs). Th­ese drives of­fer su­pe­rior speci cations to the reg­u­lar SSDs. The term EFD was coined by EMC at the be­gin­ning of 2008 to help them iden­tify SSD pro­duc­ers that could pro­vide drives with bet­ter than the stan­dard speci cations. The caveat here is that there is no gov­ern­ing body over­see­ing the EFD stan­dard and so any SSD man­u­fac­turer can claim the EFD moniker whether it of­fers bet­ter than stan­dard speci cations or not.

If you peek in­side an SSD, the ma­jor parts you will nd are the con­troller, which in­cludes the elec­tron­ics that bridge the NAND me­mory com­po­nents to the SSD in­put/out-

put in­ter­face. This is an em­bed­ded pro­ces­sor that ex­e­cutes rmware-level soft­ware and it plays a ma­jor role in de­ter­min­ing the per­for­mance level of the SSD.

An SSD also con­tains a cache. If it is of the ash va­ri­ety, it uses a small amount of DRAM as cache, which is sim­i­lar to the cache in an HDD. While the drive is op­er­at­ing a di­rec­tory of block place­ment and wear lev­el­ling date is also kept in the cache.

High per­for­mance SSDs also in­cor­po­rates a ca­pac­i­tor or some form of bat­tery. The pur­pose of this is to main­tain the in­tegrity of the data in the cache, which can be ushed to the drive in the event of a power fail­ure. The bet­ter SSDs are de­signed to con­tinue sup­ply­ing power even if there is a power out­age that lasts for a very long time.

The per­for­mance of an SSD usu­ally scales with the num­ber of par­al­lel NAND ash chips that are uti­lized in the de­vice. One NAND chip is usu­ally slow be­cause of a nar­row (8/16) asyn­chro­nous in­put/out­put in­ter­face and ad­di­tional high la­tency of the ba­sic in­put/out­put op­er­a­tions. When many NAND de­vices op­er­ate in par­al­lel in­side an SSD, the band­width scales and the high la­ten­cies can be con­cealed just so long as enough out­stand­ing op­er­a­tions are pend­ing and the load is evenly dis­trib­uted be­tween de­vices.

The more af­ford­able SSDs usu­ally em­ploy muti-level cell ash me­mory. Th­ese are slower and not as re­li­able as sin­glelevel cells. How­ever this can be mit­i­gated and in some cases even re­versed by be­ing smarter when de­sign­ing the in­ter­nal de­sign struc­ture of the SSD. Some ex­am­ples of this are in­ter­leav­ing and us­ing bet­ter, more ef cient al­go­rithms.

SSDs that are based on volatile me­mory such as DRAM are char­ac­ter­ized by faster data ac­cess, typ­i­cally un­der 10 mi­crosec­onds. Th­ese are used mainly to ac­cel­er­ate ap­pli­ca­tions that would oth­er­wise be held back by the la­tency of ash SSDs or tra­di­tional HDDs. DRAM-based SSDs usu­ally uti­lize ei­ther an in­ter­nal bat­tery or an ex­ter­nal AC/DC adapter and backup stor­age sys­tems to make sure that data is re­tained even while no power is be­ing sup­plied to the drive from ex­ter­nal sources. In the event of a power out­age the bat­tery sup­plies power while all in­for­ma­tion is copied from the RAM to the back-up stor­age. When the power is re­stored, the in­for­ma­tion is copied back to the RAM from the back-up stor­age, and the SSD re­sumes nor­mal op­er­a­tion. Th­ese types of SSD are usu­ally tted with the same type of DRAM mod­ules used in reg­u­lar PCs and servers, which al­lows them to be swapped out and re­placed with larger mod­ules.

If an SSD is made up of var­i­ous in­ter­con­nected in­te­grated cir­cuits and an in­ter­face con­nec­tor, then there is a lot more ex­i­bil­ity in de­ter­min­ing the shape of the de­vice be­cause it is now not lim­ited to the shape of ro­tat­ing me­dia drives. Some solid-state stor­age so­lu­tions come in a larger chas­sis that may even be a rack-mount form fac­tor with numer­ous SSDs in­side. They would all con­nect to a com­mon bus in­side the chas­sis and con­nect out­side the box with a sin­gle con­nec­tor.

Com­par­ing Solid State Drives to Hard Disk Drives

When com­par­ing SSDs to HDDs you have to make cer­tain al­lowances. Tra­di­tional HDD bench­marks are fo­cused on nd­ing the per­for­mance as­pects where they are weak, such as ro­ta­tional la­tency time and seek time. Since SSDs do not spin, or seek, they may show huge su­pe­ri­or­ity in such tests. On the other hand, SSDs have chal­lenges with mixed reads and writes, and it is en­tirely pos­si­ble that their per­for­mance may de­grade over time. To get a more ac­cu­rate com­par­i­son, you should test an SSD once is it lled to ca­pac­ity with data. This is be­cause a new and ‘empty’ disk is likely to show a much bet­ter write per­for­mance dur­ing the test than it would show af­ter years of use.

Some of the ad­van­tages that SSDs have over their HDD coun­ter­parts are that the former has a faster start-up than the lat­ter be­cause no spin-up is needed. SSDs also have faster random ac­cess be­cause of the ab­sence of seek­ing mo­tion which is a char­ac­ter­is­tic of the ro­tat­ing disk plat­ter, the read and write heads and the headac­tu­a­tor mech­a­nism of HDDs. SSDs also have more con­sis­tent read per­for­mance be­cause the phys­i­cal lo­ca­tion of the data is ir­rel­e­vant. They also fea­ture faster boot and ap­pli­ca­tion launch time. SSDs are also less sus­cep­ti­ble to le frag­men­ta­tion be­cause un­like HDDs, they are not sub­jected to data ac­cess degra­da­tion caused by the greater disk head seek ac­tiv­ity when it tries to nd data that is spread across many dif­fer­ent lo­ca­tions on the disc.

SSDs are also gen­er­ally a lot qui­eter in op­er­a­tional mode be­cause un­like HDDs they do not have any mov­ing parts. This is also the rea­son why they are much cooler run­ning, con­sume less power, have much higher me­chan­i­cal re­li­a­bil­ity and are able to en­dure greater shock, vi­bra­tion and tem­per­a­ture ranges and are able to op­er­ate at higher al­ti­tude. SSDs also tend to have around dou­ble the data den­sity of HDDs and elim­i­nate the need to de­frag­ment the disc from time to time.

On the ip side, SSDs with ash me­mory have a rel­a­tively lim­ited life­time and can wear out af­ter around 2 mil­lion P/E cy­cles. The life of the de­vice can be ex­tended by adopt­ing spe­cial le sys­tems or rmware de­signs that can mit­i­gate this prob­lem by spread­ing the writes over the en­tire de­vice. This tech­nique is known as wear lev­el­ling.

At the time this was writ­ten, HDDs are be­ing sold at a lower cost per gi­ga­byte than SSDs. This be­ing said, SSDs are clos­ing the gap quite quickly and at the cur­rent rate, they are ex­pected to be price com­pet­i­tive with HDDs over the next few years.

How All This Re­lates to Mu­sic

What does all this mean for mu­sic lis­ten­ers? For starters, the ever-de­creas­ing cost of stor­ing data is prov­ing to be a boost for the sales of high-res­o­lu­tion mu­sic les, es­pe­cially 24-bit/192 kHz res­o­lu­tion les, which are ex­po­nen­tially larger than their CD-qual­ity 16-bit/44 kHz coun­ter­parts. The shrink­ing size of ex­ter­nal drives is mak­ing it a lot eas­ier and more con­ve­nient to store and carry around your mu­sic les. To­day you can buy 256 gi­ga­byte thumb drives which can prob­a­bly store your en­tire mu­sic le col­lec­tion and carry it around in your pocket.

This trend is also ex­pected to has­ten the CD sys­tem’s jour­ney into ex­tinc­tion. Just a cou­ple of decades ago we mar­velled at how the CD sys­tem made it so easy to store and ac­cess our mu­sic. We now live in an age where one jump drive that ts into the palm of our hand can con­tain the same dig­i­tal mu­sic con­tent as hun­dreds of CDs!

Top: Shows the spin­ning disc and mov­able read and write head in­side a Hard Disk Drive (HDD). Bot­tom: Shows the mi­crochips found in­side a Solid State Drive (SDD); no­tice that there are no mov­ing parts here.

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