{"id":97879,"date":"2020-10-22T20:43:09","date_gmt":"2020-10-22T18:43:09","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/tehnologii-magnitnoj-zapisi-hdd-prosto-o-slozhnom"},"modified":"2020-10-22T20:43:09","modified_gmt":"2020-10-22T18:43:09","slug":"tehnologii-magnitnoj-zapisi-hdd-prosto-o-slozhnom","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sq\/blog\/administrirovanie\/tehnologii-magnitnoj-zapisi-hdd-prosto-o-slozhnom","title":{"rendered":"Teknologjit\u00eb e regjistrimit magnetik HDD: Thjesht p\u00ebr t\u00eb komplikuar\u00ebn","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"Teknologjit\u00eb
\nDisku i par\u00eb n\u00eb bot\u00eb, IBM RAMAC 305, i cili u lan\u00e7ua n\u00eb vitin 1956, kishte vet\u00ebm 5 MB t\u00eb dh\u00ebnash, peshonte 970 kg dhe kishte p\u00ebrmasat e nj\u00eb frigoriferi industrial. Sot, lider\u00ebt modern\u00eb t\u00eb korporatave mund t\u00eb mburren me kapacitet q\u00eb arrin deri n\u00eb 20 TB. Imagjinoni k\u00ebt\u00eb: 64 vjet m\u00eb par\u00eb, p\u00ebr t\u00eb regjistruar nj\u00eb sasi t\u00eb till\u00eb informacioni do t\u00eb nevojiteshin m\u00eb shum\u00eb se 4 milion RAMAC 305, dhe hap\u00ebsira e nevojshme p\u00ebr ta do t\u00eb ishte m\u00eb e madhe se 9 kilometra katror\u00eb, nd\u00ebrsa sot p\u00ebr k\u00ebt\u00eb do t\u00eb mjaftonte nj\u00eb kutiz\u00eb e vog\u00ebl me pesh\u00eb rreth 700 gram! Pjes\u00ebrisht, arritja e k\u00ebtij p\u00ebrmir\u00ebsimi t\u00eb jasht\u00ebzakonsh\u00ebm n\u00eb densitetin e ruajtjes \u00ebsht\u00eb rezultat i p\u00ebrmir\u00ebsimit t\u00eb metodave t\u00eb regjistrimit magnetik.<\/a><\/noindex>
\n\u00cbsht\u00eb e v\u00ebshtir\u00eb t\u00eb besosh, por struktura e disk\u00ebve t\u00eb fort\u00eb nuk ka ndryshuar n\u00eb m\u00ebnyr\u00eb themelore p\u00ebr gati 40 vjet, q\u00eb nga viti 1983: pik\u00ebrisht at\u00ebher\u00eb doli n\u00eb drit\u00eb disku i par\u00eb 3,5-in\u00e7 RO351, i zhvilluar nga kompania skoceze Rodime. Ky i vog\u00ebl kishte dy pllaka magnetike prej 10 MB secila, p\u00ebrkat\u00ebsisht ishte n\u00eb gjendje t\u00eb ruante dy her\u00eb m\u00eb shum\u00eb t\u00eb dh\u00ebna sesa ST-412 i p\u00ebrdit\u00ebsuar prej 5,25 in\u00e7, i l\u00ebshuar nga Seagate n\u00eb t\u00eb nj\u00ebjtin vit p\u00ebr kompjuter\u00ebt personal\u00eb IBM 5160.<\/p>\n

\"Teknologjit\u00eb
\nRodime RO351 \u2014 disku i par\u00eb n\u00eb bot\u00eb 3,5-in\u00e7<\/i><\/p>\n

Megjithat\u00eb, p\u00ebrkund\u00ebr inovacionit dhe p\u00ebrmasave kompakte, n\u00eb momentin e lansimit, RO351 doli t\u00eb ishte pothuajse i panevojsh\u00ebm p\u00ebr ask\u00ebnd, dhe t\u00eb gjitha p\u00ebrpjekjet e m\u00ebtejshme t\u00eb Rodime p\u00ebr t'u b\u00ebr\u00eb nj\u00eb em\u00ebr i njohur n\u00eb tregun e disk\u00ebve t\u00eb fort\u00eb d\u00ebshtuan, duke b\u00ebr\u00eb q\u00eb n\u00eb vitin 1991 kompania t\u00eb detyrohet t\u00eb nd\u00ebrpres\u00eb aktivitetin e saj, duke shitur pothuajse t\u00eb gjitha aktivet dhe duke reduktuar stafin n\u00eb minimum. Megjithat\u00eb, duket se Rodime nuk ishte e destinuar t\u00eb falimentonte: s\u00eb shpejti, prodhuesit m\u00eb t\u00eb m\u00ebdhenj t\u00eb disk\u00ebve t\u00eb fort\u00eb filluan t\u00eb interesoheshin p\u00ebr t\u00eb, duke d\u00ebshiruar t\u00eb blejn\u00eb licenc\u00ebn p\u00ebr t\u00eb p\u00ebrdorur formatin e patentuar nga skocez\u00ebt. Aktualisht, 3,5 in\u00e7 \u00ebsht\u00eb standardi i pranuar p\u00ebr prodhimin e HDD-ve p\u00ebr konsumator\u00eb, si dhe p\u00ebr mbajt\u00ebsit e klas\u00ebs korporative.<\/p>\n

Me pajisjet gjenetike, Deep Learning dhe interneti i gj\u00ebrave (IoT), shuma e t\u00eb dh\u00ebnave t\u00eb krijuara nga njer\u00ebzimi ka filluar t\u00eb rritet n\u00eb m\u00ebnyr\u00eb eksponenciale. Sipas vler\u00ebsimeve t\u00eb agjencis\u00eb analitike IDC, deri n\u00eb vitin 2025, sasia e informacionit q\u00eb gjenerohet nga njer\u00ebzit dhe pajisjet q\u00eb na rrethojn\u00eb do t\u00eb arrij\u00eb 175 zettabayt (1 Zbayt = 10^21 byte), dhe kjo pasiq\u00eb n\u00eb vitin 2019 numri ishte 45 Zbayt, n\u00eb 2016 \u2013 16 Zbayt, dhe n\u00eb vitin 2006, sasia totale e t\u00eb dh\u00ebnave t\u00eb prodhuara n\u00eb t\u00eb gjith\u00eb historin\u00eb e njohur nuk kalonte 0,16 (!) Zbayt. Teknologjit\u00eb moderne, p\u00ebrfshir\u00eb metodat e avancuara t\u00eb regjistrimit t\u00eb t\u00eb dh\u00ebnave, ndihmojn\u00eb n\u00eb p\u00ebrballimin e shp\u00ebrthimeve informative.<\/p>\n

LMR, PMR, CMR dhe TDMR: \u00e7far\u00eb ndryshimi ka?<\/h2>\n

\nPrincipi i funksionimit t\u00eb disqeve t\u00eb forta \u00ebsht\u00eb mjaft i thjesht\u00eb. Gjat\u00eb metalik\u00eb t\u00eb holl\u00eb, t\u00eb mbuluar me nj\u00eb shtres\u00eb materiali ferromagnetik (nj\u00eb substanc\u00eb kristaline q\u00eb mund t\u00eb ruaj\u00eb magnetizmin edhe n\u00eb munges\u00eb t\u00eb ndikimit t\u00eb nj\u00eb fushe magnetike t\u00eb jashtme n\u00eb temperatura m\u00eb t\u00eb ul\u00ebta se pika Curie) l\u00ebvizin n\u00eb raport me bllokun e kokave t\u00eb shkrimit me shpejt\u00ebsi t\u00eb madhe (5400 rrotullime n\u00eb minut\u00eb ose m\u00eb shum\u00eb). Kur l\u00ebshohet energji elektrike n\u00eb kok\u00ebn e shkrimit, krijohet nj\u00eb fush\u00eb magnetike q\u00eb ndryshon drejtimin e vektorit t\u00eb magnetizmit t\u00eb domain\u00ebve (zona discrete t\u00eb substanc\u00ebs) t\u00eb ferromagnetit. Leximi i t\u00eb dh\u00ebnave ndodh ose p\u00ebrmes fenomenit t\u00eb induksionit elektromagnetik (l\u00ebvizja e domain\u00ebve n\u00eb raport me sensorin shkakton n\u00eb t\u00eb nj\u00eb energji elektrike t\u00eb alternuar), ose p\u00ebrmes efekti gjigant t\u00eb magnetorezistenc\u00ebs (n\u00eb ndikimin e fush\u00ebs magnetike ndryshohet rezistenca elektrike e sensorit), ashtu si\u00e7 \u00ebsht\u00eb realizuar n\u00eb memorjet moderne. \u00c7do domain kode nj\u00eb bit informacioni, duke marr\u00eb vler\u00ebn logjike \"0\" ose \"1\" n\u00eb var\u00ebsi t\u00eb drejtimit t\u00eb vektorit t\u00eb magnetizmit.<\/p>\n

P\u00ebr nj\u00eb koh\u00eb t\u00eb gjat\u00eb, disqet e ngurta p\u00ebrdor\u00ebn metod\u00ebn e regjistrimit t\u00eb magnetizmit longitudinal (Longitudinal Magnetic Recording, LMR), ku vektori i magnetizimit t\u00eb domen\u00ebve ishte n\u00eb nivelin e pllak\u00ebs magnetike. Megjith\u00ebse kjo teknologji kishte nj\u00eb realizim t\u00eb relativisht thjesht\u00eb, ajo kishte nj\u00eb disavantazh t\u00eb duksh\u00ebm: p\u00ebr t\u00eb kap\u00ebrcyer koercivitetin (kalimi i grimcave magnetike n\u00eb nj\u00eb gjendje mono-domen), ishte e nevojshme t\u00eb linin nj\u00eb zon\u00eb t\u00eb konsiderueshme tampon (hap\u00ebsira e mbrojtjes \u2014 guard space) midis gjurm\u00ebve. Si rezultat, densiteti maksimal i regjistrimit q\u00eb arriti t\u00eb arrihej n\u00eb fund t\u00eb k\u00ebsaj teknologjie ishte vet\u00ebm 150 Gbit\/in\u00e72.<\/p>\n

\"Teknologjit\u00eb
\nN\u00eb vitin 2010, LMR u z\u00ebvend\u00ebsua praktikisht plot\u00ebsisht nga PMR (Perpendicular Magnetic Recording \u2014 regjistrimi magnetik perpendicular). Dallimi kryesor i k\u00ebsaj teknologjie nga regjistrimi magnetik longitudinal \u00ebsht\u00eb se vektori i orientimit magnetik t\u00eb \u00e7do domeni \u00ebsht\u00eb n\u00eb nj\u00eb k\u00ebnd prej 90\u00b0 me sip\u00ebrfaqen e pllak\u00ebs magnetike, gj\u00eb q\u00eb lejon reduktimin e ndjesh\u00ebm t\u00eb intervalit midis gjurm\u00ebve. <\/p>\n

Si rezultat, densiteti i regjistrimit t\u00eb t\u00eb dh\u00ebnave arriti t\u00eb rritej duksh\u00ebm (deri n\u00eb 1 Tbit\/in\u00e72 n\u00eb pajisjet moderne), pa sakrifikuar karakteristikat e shpejt\u00ebsis\u00eb dhe besueshm\u00ebris\u00eb s\u00eb disqeve t\u00eb ngurta. Aktualisht, regjistrimi magnetik perpendicular \u00ebsht\u00eb dominues n\u00eb treg, ndaj dhe shpesh quhet gjithashtu CMR (Conventional Magnetic Recording \u2014 regjistrimi magnetik konvencional). Duhet t\u00eb kuptohet se nuk ka asnj\u00eb ndryshim mes PMR dhe CMR \u2014 \u00ebsht\u00eb thjesht nj\u00eb variant tjet\u00ebr em\u00ebrtimi.<\/p>\n

\"Teknologjit\u00eb
\nDuke studiuar specifikimet teknike t\u00eb disqeve t\u00eb ngurta moderne, gjithashtu mund t\u00eb hasni n\u00eb nj\u00eb shkurtore misterioze TDMR. Konkrety, kjo teknologji p\u00ebrdoret nga storaget e klas\u00ebs korporative Western Digital Ultrastar seria 500<\/a><\/noindex>. Nga ana fizike, TDMR (q\u00eb shpjegohet si Two Dimensional Magnetic Recording \u2014 regjistrimi magnetik dy-dimensional) nuk ndryshon asgj\u00eb nga PMR-i i njohur: si m\u00eb par\u00eb, kemi t\u00eb b\u00ebjm\u00eb me gjurm\u00eb t\u00eb pap\u00ebrtritura, domen\u00ebt e t\u00eb cil\u00ebve jan\u00eb t\u00eb orientuar perpendicular me sip\u00ebrfaqen e pllakave magnetike. Dallimi mes teknologjive q\u00ebndron n\u00eb qasjen ndaj leximit t\u00eb informacionit.<\/p>\n

N\u00eb blokun e kokave magnetike t\u00eb disk\u00ebve t\u00eb fort\u00eb, t\u00eb krijuara me teknologjin\u00eb TDMR, secila kok\u00eb shkruese ka dy sensor\u00eb lexues q\u00eb kryejn\u00eb leximin e t\u00eb dh\u00ebnave nga \u00e7do pist\u00eb e kaluar nj\u00ebkoh\u00ebsisht. Kjo tep\u00ebrsi lejon kontrollorin e HDD t\u00eb filtroj\u00eb efektivisht zhurmat elektromagnetike, t\u00eb cilat ndodhin p\u00ebr shkak t\u00eb nd\u00ebrhyrjeve nd\u00ebrpiste (Intertrack Interference, ITI).<\/p>\n

\"Teknologjit\u00eb
\nZgjidhja e problemit me ITI ofron dy avantazhe shum\u00eb t\u00eb r\u00ebnd\u00ebsishme:<\/p>\n

    \n
  1. reduktimi i koeficientit t\u00eb nd\u00ebrhyrjes rrit densitetin e regjistrimit duke zvog\u00ebluar distanc\u00ebn midis pistave, duke siguruar nj\u00eb fitim n\u00eb kapacitetin total deri n\u00eb 10% n\u00eb krahasim me PMR-n\u00eb e zakonshme;<\/li>\n
  2. n\u00eb kombinim me teknologjin\u00eb RVS dhe mikroaktuatorin me tre pozita, TDMR-i lejon p\u00ebrballje efektive me vibracionin rotacional t\u00eb shkaktuar nga funksionimi i disk\u00ebve, q\u00eb ndihmon n\u00eb arritjen e nj\u00eb niveli stabil t\u00eb performanc\u00ebs edhe n\u00eb kushtet m\u00eb t\u00eb v\u00ebshtira t\u00eb p\u00ebrdorimit.<\/li>\n<\/ol>\n

    <\/p>\n

    \u00c7far\u00eb \u00ebsht\u00eb SMR dhe si p\u00ebrdoret?<\/h2>\n

    \nP\u00ebrmasat e kok\u00ebs shkruese jan\u00eb rreth 1.7 her\u00eb m\u00eb t\u00eb m\u00ebdha n\u00eb krahasim me p\u00ebrmasat e sensorit lexues. Kjo ndryshim i duksh\u00ebm shpjegohet mjaft thjesht: n\u00ebse moduli regjistrues b\u00ebhet edhe m\u00eb i vog\u00ebl, forcat e fush\u00ebs magnetike q\u00eb ai do t\u00eb mund t\u00eb prodhoj\u00eb do t\u00eb jen\u00eb t\u00eb pamjaftueshme p\u00ebr t\u00eb magnetizuar domenet e shtres\u00ebs ferromagnetike, dhe p\u00ebr k\u00ebt\u00eb arsye, t\u00eb dh\u00ebnat thjesht nuk do t\u00eb ruhen. N\u00eb rastin e sensorit lexues, kjo problematik\u00eb nuk paraqitet. P\u00ebr m\u00eb tep\u00ebr: miniaturizimi i tij lejon t\u00eb zvog\u00ebloj\u00eb ndikimin e ITI n\u00eb procesin e leximit t\u00eb informacionit.<\/p>\n

    Ky fakt ka sh\u00ebrbyer si baz\u00eb p\u00ebr regjistrimin e magnetik\u00ebve me \u00e7ati (Shingled Magnetic Recording, SMR). Le t\u00eb kuptojm\u00eb se si funksionon kjo. Kur p\u00ebrdoret PMR tradicionale, koha shkruese zhvendoset n\u00eb raport me \u00e7do pist\u00eb t\u00eb m\u00ebparshme p\u00ebr nj\u00eb distanc\u00eb t\u00eb barabart\u00eb me gjer\u00ebsin\u00eb e saj + gjer\u00ebsin\u00eb e hap\u00ebsir\u00ebs mbrojt\u00ebse (guard space).<\/p>\n

    \"Teknologjit\u00eb
    \nKur p\u00ebrdoret metoda e regjistrimit me pllaka, krye shkruesi zhvendoset p\u00ebrpara vet\u00ebm n\u00eb nj\u00eb pjes\u00eb t\u00eb gjer\u00ebsis\u00eb s\u00eb tij, k\u00ebshtu q\u00eb \u00e7do gjurm\u00eb e m\u00ebparshme rip\u00ebrzihet pjes\u00ebrisht nga ajo e m\u00ebposhtme: gjurm\u00ebt magnetike p\u00ebrshtaten nj\u00ebra mbi tjetr\u00ebn si pllakat e \u00e7atis\u00eb. Ky qasje lejon p\u00ebr m\u00eb shum\u00eb densitet regjistrimi, duke ofruar nj\u00eb fitim p\u00ebr kapacitet deri n\u00eb 10%, pa ndikuar negativisht n\u00eb procesin e leximit. Nj\u00eb shembull i till\u00eb mund t\u00eb sjell\u00eb     Western Digital Ultrastar DC HC 650<\/a><\/noindex> \u2014 disk\u00ebt e par\u00eb n\u00eb bot\u00eb 3.5 in\u00e7 me kapacitet 20 TB me nd\u00ebrfaqen SATA\/SAS, shfaqja e t\u00eb cil\u00ebve u b\u00eb e mundur pik\u00ebrisht fal\u00eb teknologjis\u00eb s\u00eb re t\u00eb regjistrimit magnetik. K\u00ebshtu, kalimi n\u00eb disk\u00ebt SMR lejon rritjen e densitetit t\u00eb ruajtjes s\u00eb t\u00eb dh\u00ebnave n\u00eb t\u00eb nj\u00ebjtat regjistra me kosto minimale p\u00ebr modernizimin e infrastruktur\u00ebs IT.<\/p>\n

    \"Teknologjit\u00eb
    \nMegjithat\u00eb, pavar\u00ebsisht k\u00ebtij avantazhi t\u00eb madh, SMR ka nj\u00eb disavantazh t\u00eb duksh\u00ebm. Sepse gjurm\u00ebt magnetike p\u00ebrshtaten nj\u00ebra mbi tjetr\u00ebn, gjat\u00eb p\u00ebrdit\u00ebsimit t\u00eb t\u00eb dh\u00ebnave do t\u00eb k\u00ebrkohet t\u00eb rip\u00ebrsehet jo vet\u00ebm fragmente e nevojshme, por edhe t\u00eb gjitha gjurm\u00ebt e m\u00ebpasme brenda diskut magnetik, i cili mund t\u00eb ket\u00eb nj\u00eb kapacitet q\u00eb kalon 2 terabajt, \u00e7ka merr me vete nj\u00eb r\u00ebnie t\u00eb r\u00ebnd\u00eb t\u00eb performanc\u00ebs.<\/p>\n

    Zgjidhja e k\u00ebsaj problematike ndihmohet nga bashkimi i nj\u00eb numri t\u00eb caktuar gjurm\u00ebsh n\u00eb grupe t\u00eb ve\u00e7anta, t\u00eb quajtura zona. Edhe pse ky qasje p\u00ebr organizimin e ruajtjes s\u00eb t\u00eb dh\u00ebnave pakson kapacitetin e p\u00ebrgjithsh\u00ebm t\u00eb HDD (pasi duhet ruajtur hapa t\u00eb mjaftuesh\u00ebm midis zonave p\u00ebr t\u00eb parandaluar rip\u00ebrgjigjen e gjurm\u00ebve nga grupet fqinje), kjo ndihmon p\u00ebr t\u00eb p\u00ebrshpejtuar procesin e p\u00ebrdit\u00ebsimit t\u00eb t\u00eb dh\u00ebnave, sepse tani merr pjes\u00eb vet\u00ebm nj\u00eb num\u00ebr i kufizuar gjurm\u00ebsh.<\/p>\n

    \"Teknologjit\u00eb
    \nRegjistrimi me pllaka magnetike parashikon disa opsione t\u00eb realizimit:<\/p>\n