{"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\u00eb 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 lancuar n\u00eb vitin 1956, kishte kapacitet prej vet\u00ebm 5 MB, peshonte 970 kg dhe kishte p\u00ebrmasa krahasuese me nj\u00eb frigorifer industrial. Sot, lider\u00ebt e korporatave mund t\u00eb mburren me kapacitet deri n\u00eb 20 TB. Mendojini: 64 vjet m\u00eb par\u00eb, p\u00ebr t\u00eb ruajtur nj\u00eb sasi t\u00eb till\u00eb informacioni, do t\u00eb nevojiteshin m\u00eb shum\u00eb se 4 milion RAMAC 305, dhe sip\u00ebrfaqja e qendr\u00ebs s\u00eb t\u00eb dh\u00ebnave t\u00eb nevojshme p\u00ebr t'i akomoduar ata do t\u00eb kalonte 9 kilometra katror\u00eb, nd\u00ebrsa sot p\u00ebr k\u00ebt\u00eb do t\u00eb mjaftonte nj\u00eb kuti e vog\u00ebl me pesh\u00eb rreth 700 gram! Pjes\u00ebrisht, kjo rritje e jasht\u00ebzakonshme n\u00eb densitetin e ruajtjes \u00ebsht\u00eb arritur p\u00ebrmes p\u00ebrmir\u00ebsimit t\u00eb metodave t\u00eb regjistrimit magnetik.<\/a><\/noindex>
\n\u00cbsht\u00eb e v\u00ebshtir\u00eb t\u00eb besosh, por koncepti baz\u00eb i disqeve t\u00eb forta nuk ka ndryshuar p\u00ebr gati 40 vjet, duke filluar nga viti 1983: pik\u00ebrisht at\u00ebher\u00eb erdhi n\u00eb jet\u00eb disku i par\u00eb 3.5-in\u00e7 RO351, i zhvilluar nga kompania skoceze Rodime. Ky vog\u00eblush kishte dy pllaka magnetike me nga 10 MB secila, dometh\u00ebn\u00eb ishte n\u00eb gjendje t\u00eb ruante dyfishin e t\u00eb dh\u00ebnave n\u00eb krahasim me ST-412 t\u00eb p\u00ebrdit\u00ebsuar, i cili ishte 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

Megjith\u00ebse ishte inovativ dhe kompakt, n\u00eb momentin e lan\u00e7imit RO351 doli t\u00eb ishte praktikisht i panevojsh\u00ebm, dhe t\u00eb gjitha p\u00ebrpjekjet e m\u00ebtejshme t\u00eb Rodime p\u00ebr t'u vendosur n\u00eb tregun e hard disqeve d\u00ebshtuan, \u00e7ka e detyroi kompanin\u00eb t\u00eb ndalonte aktivitetin e saj n\u00eb vitin 1991, duke shitur pothuajse t\u00eb gjitha asetet dhe duke e zvog\u00ebluar stafin deri n\u00eb minimum. Megjithat\u00eb, Rodime nuk u fatkeq\u00ebsua p\u00ebr t'u deklaruar n\u00eb falimentim: shum\u00eb shpejt, filluan t\u00eb k\u00ebrkonin licenc\u00ebn p\u00ebr t\u00eb p\u00ebrdorur formati t\u00eb patentuar nga skocez\u00ebt prodhuesit m\u00eb t\u00eb m\u00ebdhenj t\u00eb hard disqeve. Aktualisht, 3.5 in\u00e7 \u00ebsht\u00eb standardi i pranuar p\u00ebr prodhimin e HDD-ve dhe ruajt\u00ebsve t\u00eb klas\u00ebs korporative.<\/p>\n

Me ndodhin avancimet n\u00eb rrjetin nervor, Deep Learning dhe Internetin e Dingeve (IoT), sasia 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 t\u00eb gjeneruar si nga njer\u00ebzit ashtu edhe nga pajisjet rreth nesh do t\u00eb arrij\u00eb 175 zettabajt (1 ZB = 10^21 byte), nd\u00ebrkoh\u00eb q\u00eb n\u00eb vitin 2019 kjo ishte 45 ZB, n\u00eb vitin 2016 \u2013 16 ZB, dhe n\u00eb vitin 2006, sasia totale e t\u00eb dh\u00ebnave t\u00eb prodhuara p\u00ebr t\u00eb gjith\u00eb historin\u00eb e njohur nuk e kalonte 0,16 (!) ZB. Teknologjit\u00eb e avancuara, duke p\u00ebrfshir\u00eb metodat e p\u00ebrmir\u00ebsuara t\u00eb regjistrimit t\u00eb t\u00eb dh\u00ebnave, ndihmojn\u00eb p\u00ebr t\u00eb p\u00ebrballuar k\u00ebt\u00eb shp\u00ebrthim informacioni.<\/p>\n

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

\nPrincipi i funksionimit t\u00eb disqeve t\u00eb fort\u00eb \u00ebsht\u00eb mjaft i thjesht\u00eb. Plakat e holla metalike, t\u00eb mbuluara me nj\u00eb shtres\u00eb materiale ferromagnetike (nj\u00eb substanc\u00eb kristalike q\u00eb mund t\u00eb ruaj\u00eb magnetizimin edhe n\u00eb munges\u00eb t\u00eb fush\u00ebs magnetike t\u00eb jashtme n\u00eb temperatura m\u00eb t\u00eb ulta se pika Curie) l\u00ebvizin n\u00eb lidhje me bllokun e kokave t\u00eb shkrimit me nj\u00eb shpejt\u00ebsi t\u00eb madhe (5400 rrotullime n\u00eb minut\u00eb ose m\u00eb shum\u00eb). Kur aplikohet nj\u00eb rrym\u00eb elektrike n\u00eb kok\u00ebn e shkrimit, krijohet nj\u00eb fush\u00eb magnetike e alternuar, e cila ndryshon drejtimin e vektorit t\u00eb magnetizimit t\u00eb domain\u00ebve (zona diskrete 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 lidhje me sensorin shkakton krijimin e nj\u00eb rryme elektrike t\u00eb alternuar n\u00eb k\u00ebt\u00eb t\u00eb fundit), ose p\u00ebrmes efektit gjigand magnetorrezistiv (n\u00eb ndikimin e fush\u00ebs magnetike, ndryshohet q\u00ebndrushm\u00ebria elektrike e sensorit), si\u00e7 realizohet n\u00eb ruajt\u00ebsit modern\u00eb. \u00c7do domain kodon 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 magnetizimit.<\/p>\n

P\u00ebr nj\u00eb koh\u00eb t\u00eb gjat\u00eb, disqet e forta p\u00ebrdornin metod\u00ebn e regjistrimit magnetik longitudinal (Longitudinal Magnetic Recording, LMR), ku vektori i magnetizmit t\u00eb domain\u00ebve kishte nj\u00eb plan n\u00eb sip\u00ebrfaqen e pllak\u00ebs magnetike. Megjith\u00ebse kjo teknologji ishte relativisht e thjesht\u00eb p\u00ebr t'u zbatuar, ajo kishte nj\u00eb disavantazh t\u00eb r\u00ebnd\u00ebsish\u00ebm: p\u00ebr t\u00eb luftuar koercivitetin (kalimi i grimcave magnetike n\u00eb nj\u00eb gjendje nj\u00eb-domaini), duhej t\u00eb mbeteshin zona t\u00eb konsiderueshme buffer (t\u00eb ashtuquajturat guard space \u2014 hap\u00ebsira mbrojt\u00ebse) midis shenjave. Si pasoj\u00eb, densiteti maksimal i regjistrimit q\u00eb u arrit n\u00eb fund t\u00eb k\u00ebsaj teknologjie ishte vet\u00ebm 150 Gbit\/d\u00ebrras\u00eb\u00b2.<\/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 domaini \u00ebsht\u00eb n\u00eb nj\u00eb k\u00ebnd prej 90\u00b0 me sip\u00ebrfaqen e pllak\u00ebs magnetike, e cila lejon nj\u00eb reduktim t\u00eb konsideruesh\u00ebm t\u00eb intervaleve midis shenjave. <\/p>\n

K\u00ebshtu, densiteti i regjistrimit t\u00eb t\u00eb dh\u00ebnave \u00ebsht\u00eb rritur ndjesh\u00ebm (deri n\u00eb 1 Tbit\/dm\u00b2 n\u00eb pajisjet moderne), pa kompromise n\u00eb karakteristikat e shpejt\u00ebsis\u00eb dhe besueshm\u00ebris\u00eb s\u00eb disk\u00ebve t\u00eb fort\u00eb. Aktualisht, regjistrimi magnetik periferik \u00ebsht\u00eb dominues n\u00eb treg, ndaj shpesh quhet edhe CMR (Conventional Magnetic Recording \u2014 regjistrimi magnetik konvencional). Duhet kuptuar se nuk ka asnj\u00eb ndryshim real midis PMR dhe CMR \u2014 \u00ebsht\u00eb thjesht nj\u00eb variant tjet\u00ebr emri.<\/p>\n

\"Teknologjit\u00eb
\nDuke studiuar specifikat teknike t\u00eb disqeve t\u00eb fort\u00eb modern\u00eb, mund t\u00eb hasni n\u00eb abbreviatur\u00ebn misterioze TDMR. Konkr\u00ebt\u00ebsisht, kjo teknologji p\u00ebrdoret nga ruajt\u00ebsit e klas\u00ebs korporative. Western Digital Ultrastar seria 500<\/a><\/noindex>. Nga pik\u00ebpamja fizike, TDMR (q\u00eb do t\u00eb thot\u00eb Two Dimensional Magnetic Recording \u2014 regjistrimi magnetik dy dimensional) nuk ndryshon nga PMR q\u00eb njohim: si m\u00eb par\u00eb, kemi t\u00eb b\u00ebjm\u00eb me pista q\u00eb nuk p\u00ebrputhen, me domenet q\u00eb orientohen perpendikular ndaj planeve magnetike. Dallimi midis teknologjive q\u00ebndron n\u00eb qasjen ndaj leximit t\u00eb t\u00eb dh\u00ebnave.<\/p>\n

N\u00eb bllokun e kokave magnetike t\u00eb hard disk\u00ebve, t\u00eb krijuar me teknologjin\u00eb TDMR, p\u00ebr \u00e7do kok\u00eb shkrimi ka dy sensor\u00eb lexues, t\u00eb cil\u00ebt kryejn\u00eb leximin e dh\u00ebnave nga \u00e7do gjurm\u00eb t\u00eb kaluar nj\u00ebkoh\u00ebsisht. Kjo tep\u00ebrsi i mund\u00ebson kontrollorit HDD t\u00eb filtroj\u00eb n\u00eb m\u00ebnyr\u00eb efektive zhurmat elektromagnetike, t\u00eb cilat shkaktohen nga nd\u00ebrhyrja nd\u00ebrmjet gjurm\u00ebve (Intertrack Interference, ITI).<\/p>\n

\"Teknologjit\u00eb
\nZgjidhja e problemit me ITI ofron dy p\u00ebrfitime tep\u00ebr t\u00eb r\u00ebnd\u00ebsishme:<\/p>\n

    \n
  1. reduktimi i koeficientit t\u00eb interferenc\u00ebs lejon rritjen e densitetit t\u00eb regjistrimit p\u00ebrmes zvog\u00eblimit t\u00eb distanc\u00ebs midis gjurm\u00ebve, duke siguruar nj\u00eb p\u00ebrfitim n\u00eb kapacitetin e p\u00ebrgjithsh\u00ebm deri n\u00eb 10% krahasuar me PMR t\u00eb zakonsh\u00ebm;<\/li>\n
  2. n\u00eb p\u00ebrputhje me teknologjin\u00eb RVS dhe mikroaktorin me tre pozita, TDMR mund\u00ebson p\u00ebrballjen efektive me vibracionin rotativ, t\u00eb shkaktuar nga puna e hard disk\u00ebve, \u00e7ka ndihmon n\u00eb arritjen e nj\u00eb niveli t\u00eb q\u00ebndruesh\u00ebm t\u00eb performanc\u00ebs edhe n\u00eb kushtet m\u00eb t\u00eb v\u00ebshtira t\u00eb pun\u00ebs.<\/li>\n<\/ol>\n

    <\/p>\n

    \u00c7far\u00eb \u00ebsht\u00eb SMR dhe me \u00e7far\u00eb merret?<\/h2>\n

    \nDimensionet e kok\u00ebs s\u00eb shkrimit jan\u00eb rreth 1.7 her\u00eb m\u00eb t\u00eb m\u00ebdha krahasuar me dimensionet e sensorit lexues. Kjo diferenc\u00eb e konsiderueshme shpjegohet mjaft thjesht\u00eb: n\u00ebse moduli shkrues do t\u00eb b\u00ebhej edhe m\u00eb fisnik, forcat e fush\u00ebs magnetike q\u00eb ai do t\u00eb ishte n\u00eb gjendje t\u00eb gjeneronte do t\u00eb ishin t\u00eb pamjaftueshme p\u00ebr magnetizimin e domaineve t\u00eb shtres\u00ebs ferromagnetike, dhe si rezultat, t\u00eb dh\u00ebnat thjesht nuk do t\u00eb ruhej. N\u00eb rastin e sensorit lexues, nj\u00eb problem i till\u00eb nuk lind. M\u00eb tep\u00ebr, miniaturizimi i tij lejon t\u00eb zvog\u00eblohet edhe m\u00eb tej ndikimi i p\u00ebrmendur m\u00eb par\u00eb t\u00eb ITI n\u00eb procesin e leximit t\u00eb informacionit.<\/p>\n

    Ky fakt \u00ebsht\u00eb thelb\u00ebsor p\u00ebr regjistrimin magnetik t\u00eb pllakave (Shingled Magnetic Recording, SMR). Le t\u00eb kuptojm\u00eb si funksionon. Kur p\u00ebrdoret PMR tradicional, koka e shkrimit l\u00ebviz n\u00eb krahasim me \u00e7do shteg t\u00eb m\u00ebparsh\u00ebm n\u00eb 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
    \nDuke p\u00ebrdorimit t\u00eb metod\u00ebs s\u00eb regjistrimit me pllaka, kok\u00eb shkruese zhvendoset p\u00ebrpara vet\u00ebm n\u00eb nj\u00eb pjes\u00eb t\u00eb gjer\u00ebsis\u00eb s\u00eb saj, k\u00ebshtu q\u00eb \u00e7do gjurm\u00eb e m\u00ebparshme p\u00ebrfundon duke u regjistruar pjesalisht nga e ardhmja: gjurm\u00ebt magnetike mbivendosen si pllakat e \u00e7atis\u00eb. Ky qasje lejon nj\u00eb rritje t\u00eb densitetit t\u00eb regjistrimit, duke siguruar nj\u00eb fitim t\u00eb kapacitetit deri n\u00eb 10%, pa ndikuar procesin e leximit. Si shembull mund t\u00eb p\u00ebrmendim     Western Digital Ultrastar DC HC 650<\/a><\/noindex> \u2014 disqet e para n\u00eb bot\u00eb 3.5-inch me kapacitet prej 20 TB me interface SATA\/SAS, shfaqja e t\u00eb cilave u b\u00eb e mundur pik\u00ebrisht fal\u00eb teknologjis\u00eb s\u00eb re t\u00eb regjistrimit magnetik. K\u00ebsisoj, kalimi n\u00eb disqe SMR lejon rritjen e densitetit t\u00eb ruajtjes s\u00eb t\u00eb dh\u00ebnave n\u00eb t\u00eb nj\u00ebjtat raft\u00eb me investime minimale p\u00ebr modernizimin e Infrastruktur\u00ebs IT.<\/p>\n

    \"Teknologjit\u00eb
    \nMegjith\u00ebse ka nj\u00eb avantazh t\u00eb till\u00eb t\u00eb r\u00ebnd\u00ebsish\u00ebm, SMR ka edhe nj\u00eb disavantazh t\u00eb duksh\u00ebm. Duke qen\u00eb se shtresat magnetike mbivendosen, gjat\u00eb p\u00ebrdit\u00ebsimit t\u00eb t\u00eb dh\u00ebnave, k\u00ebrkohet q\u00eb t\u00eb shkenkohen jo vet\u00ebm fragmenti i k\u00ebrkuar, por edhe t\u00eb gjitha pistat pas tij brenda pllak\u00ebs magnetike, e cila mund t\u00eb kaloj\u00eb 2 terabajt, gj\u00eb q\u00eb e rrezikon ndjesh\u00ebm performanc\u00ebn.<\/p>\n

    Zgjidhja e k\u00ebsaj problemi ndihmohet nga grumbullimi i nj\u00eb numri t\u00eb caktuar pistash n\u00eb grupe t\u00eb ve\u00e7anta, t\u00eb quajtura zona. Edhe pse ky qasje n\u00eb organizimin e ruajtjes s\u00eb t\u00eb dh\u00ebnave paksa e ul kapacitetin total t\u00eb HDD (pavar\u00ebsisht se midis zonave duhet t\u00eb mbahen hap\u00ebsira mjaft t\u00eb m\u00ebdha, p\u00ebr t\u00eb parandaluar rishk\u00ebrkimin e pistave nga grupet fqinj\u00eb), kjo ndihmon p\u00ebr t\u00eb p\u00ebrshpejtuar ndjesh\u00ebm procesin e p\u00ebrdit\u00ebsimit, pasi tani p\u00ebrfshihen vet\u00ebm disa pista t\u00eb kufizuara.<\/p>\n

    \"Teknologjit\u00eb
    \nRegjistrimi magnetik i \u00e7atis\u00eb parashikon disa variante implementimi:<\/p>\n