High-Availability (N8900, N12000 Series/N16000 Series Only) - Thecus N8900 series User Manual

To enable t his opt ion, t he init iat or can connect wit h " Dat a digest " and " Header
digest " .
M a x Conn e ct ions
The m axim um num ber of iSCSI connect ions.
Er r or Re cove r y Le ve l
The Er ror Recov er y Lev el ( ERL) is negot iat ed during a leading iSCSI connect ion
login in t radit ional iSCSI ( RFC 3720) and iSER ( RFC 5046) .
ERL= 0 : Se ssion Re cove r y
ERL= 0 ( Session Recov ery) is t rigger ed when failures wit hin a com m and,
wit hin a connect ion, and/ or wit hin TCP occur. This causes all of t he previous
connect ions fr om t he failed session t o be r est art ed on a new session by
sending a iSCSI Login Request wit h a zero TSI HRest art all iSCSI connect ions
on any failure.
ERL= 1 : D ige st Fa ilu r e Re cov e r y
ERL= 1, only applies t o t radit ional iSCSI . For iSCSI / SCTP ( which has it s own
CRC32C) and bot h t ypes of iSER ( so far) , handling header and dat a check sum
recovery can be disabled.
ERL= 2 : Con ne ct ion Re cove r y
ERL= 2, allows for bot h single and m ult iple com m unicat ion pat h sessions
wit hin a iSCSI Nexus ( and hence t he SCSI Nex us) t o act ively perform
realligence/ ret ry on iSCSI I TTs from failed iSCSI connect ions. ERL= 2 allows
iSCSI fabrics t o t ak e advant age of recovery in all regards of t ransport level
fabric failures, and in a com plet ely OS independent fashion ( i.e. below t he host
OS st orage st ack) .

High-Availability (N8900, N12000 series/N16000 series only)

HA k eeps y our dat a act ive on t w o separat e syst em s, Thecus Support s
Act ive/ Passive HA — pr ovides a fully redundant inst ance of each node, w hich is only
brought online when it s associat ed prim ary node fails.
H A se t up pr oce dur e :
HA needs t wo id e n t ica l Thecus syst em s ( sam e m odels and sam e hard disk slot
inst alled) which ar e capable for high availabilit y feat ur es. One needs t o be set up as
" Prim ary" and t he second unit as " Secondar y" , bot h unit s' needs t o hav e t he RAI D
volum e build up prior inst allat ion.
117