A Lookahead Read Cache: Improving Read Performance of Deduplication Storage for Backup Applications

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1 A Lkh R Ch: Ipvig R P Dupliti Stg Bkup Appliti Dghul Pk, Yug Ji N Dvi H.C. Du Uivity it Twi Citi, ipli, N, USA Dgu Uivity, Gyg, Gygbuk, KOREA 72-7 Eil: {pk, yugji, u}@.u.u Abtt Dt upliti ht, up i pil t pi thiqu h b wily pt pilly i bkup tg yt with th piy i bkup ti vig wll tg vig. Thu, t th titil up h h u th wit p ipvt uig th up p whil vy littl t h b t p. Hwv, th p i up bkup tg i l uil iu wh it t th tg vy yt h. I thi pp, w wly ig h i up tg bkup ppliti t ipv p by tkig vtg it pil htiti: th qu i th th wit qu. Thu, btt h utilizti, w vit th t ti with llt utu th h by lkig h thi utu i vig wiw. v, T hiv btt h p, u ig iti ll lg bu t juiiuly iti utu t huk. Ou xpit with l wl wkl tt tht u pp h h k big tibuti t p ipvt. Kyw-upliti, up, h, p. I. INTRODUCTION AND OTIVATIONS Digitl t xpli pw t upliti ht, up t hv b i th ptlight v 8% pi wig thi ttti t up thlgi []. Dt up i piliz thiqu t liit uplit t tht it ti ly uiqu t tg pl ut t with pit t th uiqu t tw. Th y, up thlgi hv b wily ply ptiully i y tg yt t bkup hiv u t ibl t i.., ti wll p vig. Thu, j hv b tly lt t wit p ipvt thby iitly ttig vig y uplit pibl with th hlp iit t hukig, ix ptiizti/hig, pi, t ti ig [2], [3], [], [], [6]. O th th h, it p h t ttt ibl ttti t h bu pti ly ivk i uh up tg yt. Hwv, wh it t yt vy h, it h igiitly it ty. Lg t igitl pvti LTDP uiti w tly vy phti th ipt p i up tg [7], [8]. v, piy tg yt hv tt t quip th up thlgi []. Althugh thi p wll wit p i l uil t i up tg, vy littl t h b t thi iu. Typil t huk glly, w KB p i y up tg llw: it, th up tg yt itii th t ti ID tiig th pig t huk t b. Th, it lk up th ti glly, 2 B i th h. O hittig th h, it th huk th h. Othwi, it th whl ti th ulyig tg th it th pig t huk i th ti. Hwv, th p ult i lw h utilizti bu v thugh th xit ptil llity i th t ti, ly ptil t huk i th ti tly []. Futh, th high up t, th high t gtti t. Thi lw ptil llity tht it w h utilizti. Ou ky i, i thi pp, li i xplitig utu ptt t huk. I gl, qu itil t wit qu i th up tg bkup. Ipi by thi pil htiti iht i uh ppliti, u h ig tk vtg utu ptt uig up p, but gl h lgith uh LRU t i thi pil tu i up hi. B th bvti, w pp lkh h ig i up tg bkup ppliti. I thi pp, w k th llwig i tibuti: Explitig Futu A: W iti iti utu uig up i.., wit p. Thu, u pp ig vit viti with llt utu ut th h. Dig Exti with Lg Bu: W ig pti h p it lg bu whih tivly iti utu huk th bi u ht t itiiti h. Extiv Dtt Alyi: Ou pp ig i utlly ipi by u iv l tt ly. Si u pp ig i h h, ulik ltiv upliti/upliti pph tht llw ptil t upliti t ipv p whil hutig it wit p, u ig t ly t hut wit p t ll, but l b ppli t th up yt. Th i thi pp i giz llw. Sti II xpli th ig pti u pp h h. Sti III pvi vity u xpitl ult ly. Sti IV iu lt wk ig pilly up p iu. Filly, Sti V iu u utu wk. II. LOOKAHEAD READ CACHE DESIGN A. Rtil Aupti I gl, uplit liit iig t t, th p t i k tt t it g wit p u t th high

2 i t i t Tbl I: Viu up gi ti DGR i uiv vi h bkup tt Uit:%. DGR pt th ti t vig iz t igil t iz. v- v-2 v-3 v- v- vg. DGR h t i 3 t 2 = 6 2 b u Figu : Ditibuti th ub ti ix l bkup tt. X-xi pt th ptg huk i ti. liklih th h t gtti []. Thi i th utl hllgig iu th t btw p wit p i up tg. T thi p iu, w pp vl h ig lvgig utu iti. I up tg bkup hiv, th qu i highly likly t b itil t it wit qu. B thi ky vti, u pp h wit tt iti th utu uig h up p, whih bl u lkh h t xplit utu. W u tht h t huk iz i vibl t ti tiig y glly, 2-3 t huk i bi uit. B. Dtt Alyi W xtiv lyi ix l bkup tt l bv tht ibl pti t i, i gl, uplit h vi bkup tt Tbl I. Thi ipli th up h b ply utiliz i gl h ig bu ly ll ub t huk i t ti. Figu xhibit th itibuti th ub t ti with pt t th ptg huk i th h ti h l bkup tt. Tht i, w bv hw y t huk i h ti wh uplit t huk qut t. Wh w h ptg iv t: lgithi l X-xi, it t t th ub t ti. Thi ipli t th t ti ly l th % t huk i h ti. Th, w pt % u iitil ht thhl vlu. Figu 2 b hw ti ptt th up bkup tt. Th X-xi pt huk qu ID uiv vi h bkup tt. Th Y-xi pt ti ID tig huk D I v T v Y 2 v ^ 3 v v h t t h u k q u ID - D I v ž v 2 t t h u k q u ID b -6 Figu 2: Cti ptt typil up. Cut t huk t... 3 vig Wiw Ht Dt Itiiti Hh_Futi Cti_IDChuk_ID R Ch Cti Dt Cti R Cut Ht/Cl Cti 2 COLD Cti N Figu 3: Ovll hittu u b h h. W u h t huk with l blg t th t ti. ix by th huk qu ID i th X-xi th ti ID tt z. F xpl, i tt ilu y uiqu huk, th ti ID i lily lik th it vi v- th tt -: th lututi withi th v- ti i Figu 2, wh i tt ti y uplit, th ht lutut u t gt pviu ti. Fu tt - thugh - hw iil t ptt: t th t huk uiqu i th iitil bkup vi v- th uplit huk i h uiv bkup tt Figu 2. I t, thi i typil htiti t bkup tt u t p liit, w hw ly igu -. O th th h, th th tw tt - -6 xhibit it ptt: th y uplit v i th iitil vi bkup tt. Thu, w y vtil li v i vi wll uiv vi bkup tt Figu 2b. C. Ahittul Ovviw Figu 3 hw vviw u pp b h ig up tg. Th pp h it th ky pt: utu liig wiw, ht t itiiti h, th h. Th liig wiw b thught lkh wiw t utu huk. Th t huk i it til piti i lwy i ut t huk t t ig th ut huk, th wiw tk li tw th utu by h ti. B thi liig wiw h, th ht l ii i. Ou ht

3 Cut A vig Wiw... Dt Chuk t h h 3 Ht/Cl Dt Itiiti Hh Futi h 2 Sllt Cut H / C R Ch ID: Cl ID:3 ID:2... Cti 2 Viti: llt R Ch 2 COLD Cti N I thi viti i COLD, v huk t th lg bu Lg Bu Lggig utu t huk Figu : Ahittu u xt h ig. Figu : Ahittu u ht t itiiti h. t itiiti h iti t ti ut. Wh y t huk it th h piti i th wiw, it ut th pig t ti i it by t: t ti i bi uit th huk. O th ty, i y t huk i vit th til piti i th wiw, th ut i by. I th ttl ti ut ut t huk i v th pi thhl vlu ti % withi th wiw, th pig ti i lii it ht ti, thwi, l ti. Thi ht thhl vlu w piilly iv i u wkl lyi. til hittu thi ht t itiiti h i ib i th llwig ubti II-D. Ltly, u h t th ti t pt th xitig h lgith uh LRU ARC. It, u h lt th lt tiv i.., llt ut ti viti. W will xt thi h ig by ittig ll lg bu it thi b ig t ipv p uth. D. Ht Dt Itiiti Sh Ht t itiiti ply iptt l i u h ig. Si it i ivk t h ti t huk i, it ut hiv lw puttil vh ll y upti []. T t th quit, w pt utig bl ilt ultipl hh uti iply i Figu. Tht i, th ti ti ut iplt by th utig bl ilt. Thi ht t itiiti h wk llw: whv t huk i th liig wiw t th h piti, th huk ID i vt it it ti ID th th ti ID i t hh uti w pt ultipl hh uti t u l itiiti t. Eh hh vlu p t thi bit piti i th bl ilt. Filly, h ut i i by ptivly. Siilly, utgig t huk th wiw h ut by igly. B th bi pti, itiiti ut huk, it ti ID i t hh uti u h, th, hk it pig ut i h bit piti th bl ilt. Du t th liklih hh llii, th h lwy h llt ut. I it i gt th pi thhl, th t ti i lii ht, thwi, l. E. B Dig Ou pp h i ily ig th y up tg th bkup hiv k ttpt t xplit it ti pil htiti. I iti, it bi h pliy i g by u ht t itiiti h. W iitilly ig ll 8B=2B ti h i w y i ultipl t/p vit. Ovll wkig p i ib llw: whv y t huk i, it ti ID i it itii th th ti i y t b t i th h. I th h i ull t ti, w t h viti. Ou h lt ti with llt utu ut viti. Hwv, ll t ti i th h y tu t it liiti v ti bu th wiw tiu t v w. Thu, w t upt thi ut igly, whih will u igbl vh bu th ly w ub billy, ti i th h. Ev thugh thi lgith i ipl, it ibly ipv up p utp th wily pt h lgith, LRU. Ulik u xt ig, u b ig utiliz u ht t itiiti h ily it iit ut gt, t ht t itiiti. F. Dig Exti Thi xt h ig i ipi by u bvti tt lyi. A hw i Figu, w ig pt h p it lg bu t xplit utu iti. Tht i, th ky i thi xt ig i t iti ll bu t lg utu huk b ti i vit th h i with th ht t itiiti. Thi lg bu i g by iul quu. B viti, u xt ig ttpt t liy th viti ti it ht l by uig u ht t itiiti h. I th viti ti i itii l tht i, ll ub huk i th ti will b i th utu, it iig utu huk withi th wiw i t it th lg bu. W t t ly t huk. Si w ply % u ht thhl vlu, th xiu ut t huk t b lgg i t t % th ttl t huk typilly - 2 huk i th viti ti. Hwv, i t, th ut lggig huk will b l th th thhl bu th wiw v w v ti ly th iig utu huk i th wiw t t

4 B B th lg bu. O th th h, i viti i itii ht, w jut vit th viti ti withut y lggig bu w till hiv high ti utilizti with thi ht ti i th utu. Th til thi pliy i tht i w t y iig utu huk i th ht ti it th lg bu, thy l l t th uy viti y lgg huk i th bu. / P L R U ò 2 L R U L R U ü 8 B 2 B B V i N u b / P L R U H 2 L R U L R U R 8 B X 2 B ^ B V i N u b III. PERFORANCE EVALUATION A. Expitl Stup W iplt u up tg iult th bi th DikSi iult []. Th ulyig tg ilu iiviul ik IB DNES-37W, h whih pvi tg pity 7,6,2 blk 8.GB. It i igu RAID t pvi btt p ugh tg p t t ll th huk i th bkup tt. Th tip uit iz i t t 32KB. W b u huk ixig hh ix tbl ggl-phh [2]. F wit p ut, w ig lp ti t xut th typil up u h bu it i uh ll th tg I/O ti. F th up, w u ix iz ti 2B bth h ti wit 6 tip uit, wh h iiviul ik v but 7 8 tip uit wit. W ply ix bkup tt Tbl I t i l t bkup vit. Eh tt it 2 uiv vi ull bkup t t. Th -, -2, -3 tt w bti ll Exhg Sv t. Th - ti yt t vii tl yt. Th - ilu t th /v ity i th hi. Th -6 ti t h iti with vl u. F u xpitl pup, ll th tt xpt th lt -6 w tut t b 2GB i iz t hv but,k huk i ttl. Eh tt ti huk t t by uig vibl-lgth hukig with vg huk iz 8KB. B. Expitl Rult Figu 6 hw th p LRU u b ig with viu h iz. Nt th th h iz 2,, 8 th ub t ti 2B. Thu, th h iz tw p t B h. v, u t th p liitti, w pt ly tw tt - - bu, b u xtiv tt lyi, u tt -, -2, -3, - xhibit vy iil t ptt hw lt itil ult ptt. Siilly, th th tw tt - -6 l xhibit iil ptt. Th, w jut h h bhl th th tw. A pltt i th Figu 6, u b ig hw btt p th LRU ll h iz ly with th hg h plt lgith bu u lgith xplit utu iti. Ou pp b h ipv th up p by vg.% 6.8% ptivly. Figu 7, 8,, pit th p ipvt with u xt h ig with viu iguti. Fit ll, i Figu 7, w xpl bth th ipt ht thhl vlu p ipvt u xt ig. Ht t itiiti ply iptt l i kig ii but lggig utu t P B T h = T h = 3 T h = T h = T h = 2 - b - Figu 6: LRU v. Ou B Dig 2 3 V i N u b - P B T h = T h = 3 T h = T h = T h = V i N u b b - Figu 7: B v. Exti with Div Ht Thhl L g = L g = 2 L g = 2 3 V i N u b - P L g = L g = 2 L g = 2 3 V i N u b b - Figu 8: Ipt Lg Bu Siz. huk i ti it th lg bu. Th ht thhl % tht i th ptg ttl t huk i t ti i v th %, th ti i itii ht, thwi, l. Oly i it i itii l, th iig utu huk will b lgg i th ll bu. Thu, itiutivly, th high ht thhl, th btt p bu th ub utu huk will b bl t b t i th bu. Hwv, u ig with th hig thhl th 3 t l t high p gi. I iti, w bv tht u xt ig with lg bu t ibly hiv p ipvt i -, -2, -3, - 2.3% ipvt vg. Hwv, i bth - -6, it igiitly ipv th p by vg 63.%. Th ult t th wkl htiti th tt w hv ly thi i II-B. v, Figu 8 uppt th xpitl ult i Figu 7 hw vy iil p ptt bu ll p gi u xt ig utlly igit th lg bu. W l bv tht u xt ig utp LRU by vg 6.3% i Ou liig wiw iz i th t t b iu i it ipli hw uh w lk h i th

5 8 8 P P 3 3 W i = 2 6 W i = 2 W i = V i N u b W i = W i = 2 W i = 2 3 V i N u b b - Figu : Ipt Wiw Siz. C L 6 C h L C 6 l L C 7 q L 3 C 8 v L V i N u b -3 P.. 8. C «L 6 C L C 6 L C 7 ¹ L 3 C 8 ¾ L V i N u b b - Figu : Ipt Div Ch Lg Bu Siz. I h, ttl p h plu lg bu i ix. C L t h iz lg bu iz ptivly. utu. Ittigly, it ipt i lt igbl i - thugh - bigg wiw v w th p i - -6 Figu. Thi i bu th th utu i big wiw tit h p, whih l t lw h utilizti i u h plii. Ltly, w xpl th ipt viu h lg bu iz uig th ttl h p. W vy bth h iz lg bu iz. A hw i Figu, w bv tht h iz i iptt t i - thugh -. Thu, igig p it h th it th lg bu will btt h ig i th typ tt w h -3 it - i Figu i it hw l ult. O th th h, lg lg bu h ipt th p i bth IV. RELATED WORK Zhu t l. i [] put pi ipt p i up tg, i ptiul, t vy. Thy l tht p ubttilly uig up p. Kll t l. [3] pp ltiv upliti h I/O Dupliti t i th /wit p by uig ik h vt. Thy uggt tt-b h ig bth wit qut pt thi up h, but it w iplt i pt h vitul il yt h ly jut pt th xitig h plt lgith uh LRU ARC. N t l. i [] itu iit th g p huk gtti lvl CFL bv tg lti btw th CFL vlu th p u bkup tt. Rtly, Siiv t l. [] pp piy ili up yt ig idup. idup ti t xplit bth ptil llity by ltivly uplitig piy t tpl llity by itiig up tt pltly i y, t ik. Hwv, it i t th il yt h ig. V. FUTURE WORK Thi wk h u tht th bi uit i y up tg i t ti tiig hu ll t huk. A u utu wk, w will v uh upti tht h t huk b itly th ulyig up tg. I iti, w iig vibl ti iz ptiv h t wkl by yilly hgig th ht thhl. Futh, w igig vl up yt whih pvi gut p whil uig ugh wit p i up tg. Ultitly, w pl t bi bth ig u plt up yt t hiv bth g p wit p. REFERENCES [] K. Siiv, T. Bi, G. G, K. Vugti, idup: Lty-w, ili t upliti piy tg, i Pig th th USENIX C Fil Stg Thlgi FAST, Fbuy 22. [2] W. Dg, F. Dugli, K. Li, H. Ptt, S. Ry, P. Shil, T i lbl t utig upliti lut, i Pig th th USENIX Fil Stt Thlgi FAST, 2. [3] C. Dubiki, L. Gyz, L. Hlt,. Kzzyk, W. Kili, P. Stzlzk, J. Szzpkwki, C. Uguu,. Wliki, HYDRAt: A lbl y tg, i Pig th 7th USENIX Fil Stt Thlgi FAST, 2. [] B. Dbth, S. Sgupt, J. Li, ChukSth: Spig up ili tg upliti uig lh y, i Pig USENIX Aul Thil C ATC, 2. [] B. Zhu, K. Li, H. Ptt, Aviig th ik bttlxt i th t i upliti il yt, i Pig th 6th USENIX Fil Stg Thlgi FAST, 28. [6] D. y W. Blky, A tuy ptil upliti, i Pig th th USENIX Fil Stt Thlgi FAST, 2. [7] LTDP R l, [8] SNIA Digitl Pvti Cpity Optiizti, [] D. Ky. yb, Apt upliti, SNIA Spig 2 Tutil, 2. [] D. Pk D. Du, Ht Dt Itiiti Flhb Stg Syt uig ultipl Bl Filt, i Pig th 27th IEEE Sypiu Stg Syt Thlgi SST, y 2. [] DikSi v.., [2] Sphh, [3] R. Kll R. Rju, I/O Dupliti: Utilizig tt iility t ipv I/O p, i Pig th 8th USENIX Fil Stg Thlgi FAST, 2. [] Y. N, G. Lu, N. Pk, W. Xi, D. Du, Chuk Fgtti Lvl: A tiv iit p gti i upliti tg, i Pig IEEE Ittil Sypiu Av High P Cputig Ntwkig AHPCN, 2.