Tölvumál - 01.01.2007, Síða 35
T Ö LV U M Á L | 3 5
Skv. SNIA má skipta þessum lausnum upp í þá flokka sem sjá má á Mynd 1.
Mynd 1-1 SNIA Block Aggregation Model
,,SAN-based” þar sem það getur farið fram í gagnanetinu sjálfu og að lokum
,,Device based” þar sem það fer fram í stýringunni sjálfri. Allar þessar lausnir
eiga það sameiginlegt að geta spannað meira en eina stýringu eða einstaka
gagnamiðlara og því flokkast stýring sem eingöngu býr til sýndarumhverfi
innan einnar stýringar ekki sem ,,Storage Virtualization” skv. skilgreiningu
SNIA (Ekki frekar en RAID skv. sömu skilgreiningu).
Eitt umsjónarumhverfi
Auk þess að leysa vandamál tengd SAN-eyjum eins og lýst hefur verið hér
að ofan er meiri ávinningur af SAN lausnum sem vert er að nefna. Í sýndar-
gagnaumhverfi líta margir gagnamiðlarar út sem ein auðlind frá bæjardyrum
netþjónsins og umsjónarmannsins. Hann þarf ekki að kunna á margs konar
umsjónarhugbúnað til að stjórna þessum gagnamiðlurum, heldur er aðeins
eitt umsjónarumhverfi sem snýr að sýndarumhverfinu.
Einfaldari og hagkvæmari rekstur með sýndar-gagnaumhverfi
Í sýndar-gagnaumhverfi er mun auðveldara að eiga við þann ofurvöxt sem
flest fyrirtæki eiga við að etja í sínum gagnaumhverfum. Komi að því að
tiltekinn gagnamiðlari fyllist, eða taka eigi hann úr þjónustu er afar einfalt
mál að flytja öll gagnasvæði af honum, án þess að komi til rekstrarstöðvunar
tengdra netþjóna. Að sama skapi er mun auðveldara að tryggja uppitíma
Sigurður H. Ólafsson
Vörustjóri gagnageymslulausna hjá Nýherja
og aðgengi að gögnum. Flestir þeir sem reka einhvers konar SAN tengda
gagnamiðlara þekkja það að þurfa að taka þá niður vegna einhverskonar
viðhalds eða uppfærslu. Þó aðgerðin sjálf taki stuttan tíma er það veruleg
röskun á rekstrarumhverfinu því einnig þarf að taka niður alla netþjóna sem
tengjast umhverfinu. Sé gagnamiðlarinn hluti af sýndarumhverfi kemur þetta
ekki niður á rekstri því einfalt mál er að flytja gögnin yfir á aðra gagnamiðlara
í umhverfinu.
Sýndarumhverfið býður einnig upp á sameiginlegan grundvöll fyrir ýmsar
aðgerðir (Advanced Copy Functions). Má nefna stöðumyndir (Point in Time
Copy/Snapshot) eða speglun á milli staða (Remote Mirroring). Þá fara þessar
aðgerðir fram í sýndarlaginu og eru þ.a.l. ekki háðar gerð eða framleiðanda
gagnamiðlararns, auk þess sem hægt er að taka t.d. stöðumyndir á milli
mismunandi og jafnvel ólíkra gagnamiðlara. Flestir stærstu framleiðendur
gagnageymslulausna eru komnir með sýndarlausnir, eða nálægt því að
koma með þær á markað í dag og fróðlegt verður að fylgjast með því hverju
fram vindur í þessum efnum.
Heimildir:
http://www.snia.org
http://www.ibm.com/servers/storage/software/virtualization
File/record subsystem
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