Tölvumál - 01.01.2007, Qupperneq 34
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Augljós kostur SAN var fl estum ljós þar sem áður höfðu fl estir neþjónar
tengst sínum diskum beint (Direct Attached Storage – DASD) með
tilheyrandi óhagræði. T.d. var ekki nokkur leið að deila lausu diskaplássi á
einum netþjóni með öðrum þjónum. Þar af leiðandi mynduðust dreifðar eyjur
af lausu plássi sem aftur urðu til þess að tölvudeildir þurftu að kaupa miklu
meira af diskum en nauðsynlegt var ef samnýting væri möguleg. Hagræðið
var því augljóst en þessar lausnir voru tiltölulega dýrar og ekki á færi allra
fyrirtækja og stofnana. Þegar SAN lausnir tóku svo að lækka í verði jókst
innleiðing þeirra kannski hraðar en umsjónarmenn sáu fyrir eða réðu við og
aftur mynduðust einangraðar SAN eyjar þar sam hagræðið sem hafði áunnist
með SAN- væðingunni tók að ganga til baka.
Einfaldari umsjón með Storage Virtualization
Til að einfalda umsjón hafa framleiðendur kynnt til sögunnar lausnir sem
Nýjungar
Gríðarlegar framfarir hafa átt sér stað í miðlægum gagnageymslulausnum síðastliðin ár og skemmst
að minnast þeirra breytinga sem Storage Area Networking (SAN) hafði á gagnageymsluumhverfi
fyrirtækja um síðustu aldamót en um er að ræða gagnanet sem gerði miðlægum diskalausnum
kleift að tengjast mörgum netþjónum og dreifa plássi og álagi á milli þeirra.
gagnageymslulausnum
í
byggja á sýndargagnageymslumhverfi (Storage Virtualization). Í raun hefur
,,virtualization” í sinni einföldustu mynd verið til staðar í gagnageymslukerfum
allt frá áttunda áratugnum, þ.e. í formi RAID (Redundant Array of
Independant Disks). RAID sýnir einmitt netþjóninum annað útlit á
undirliggjandi gagnasvæði en þá hörða diska sem eru til grundavallar, hver
í sínu lagi. Storage Networking Industry Association (SNIA) skilgreinir svo
,,Storage Virtualization” eða ,,Block Aggregation” sem lausn sem slítur í
sundur lógískt umhverfi (logical view) og hlutlægt umhverfi (physical view)
gagnaumhverfi sins.
Þrír megin fl okkar Storage Virtualization
Eins og sjá má á myndinni skiptir SNIA Storage Virtualization í þrjá
grunnfl okka. Í fyrsta lagi ,,Host-based” þar sem sýndarumhverfi ð er keyrt
á netþjóninum sjálfum, t.d. í formi rekils eða ,,Device Driver”, í öðru lagi
2.tbl-31.arg.indd 14.1.2 07, 22:3434