Thank you for the informative article!
Turns out the backplane I have is SAS-216EB which has 1 expander daughterboard (SAS-216EL) attached containing 3 mini SAS ports labelled
J1,
J2,
J3. The manual states that just 1 expander is sufficient to access all 24 drives and supports cascading.
I'm probably wrong, but is it correct to say that when 2 mini-SAS cables are used to connect the 2 ports on LSI -8i HBA card to 2 of the 3 ports on the expander card, we get
- Four 6 Gb/s SAS lanes per cable, for 24 Gb/s per cable
- Eight 6 Gb/s SAS lanes between HBA and expander, for a total of 48 Gb/s between them
Additionally,
the manual states that a second expander daughterboard can be attached to the backplane for "failover and recovery". But does it also increase the bandwidth when 2 HBA and 2 expanders are used, where HBA #1 has 2 cables to expander #1, and HBA #2 and 2 cables to expander #2?
- Four 6 Gb/s SAS lanes per cable, for 24 Gb/s per cable
- Eight 6 Gb/s SAS lanes between HBA #1 and expander #1, for a total of 48 Gb/s between them
- Eight 6 Gb/s SAS lanes between HBA #2 and expander #2, for a total of 48 Gb/s between them
- Sixteen 6 Gb/s SAS lanes between both HBAs and both expanders, for a total of 96 Gb/s between them
- Assuming that an SSD has a sustained transfer rate of 500 MB/s, 24 such SSDs are required to hit the theoretical max transfer rates
Thank you!