1
SAS-Lanes and SAS-Expander quesitons
(alien.top)
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
this post was submitted on 04 Dec 2023
1 points (100.0% liked)
Homelab
371 readers
2 users here now
Rules
- Be Civil.
- Post about your homelab, discussion of your homelab, questions you may have, or general discussion about transition your skill from the homelab to the workplace.
- No memes or potato images.
- We love detailed homelab builds, especially network diagrams!
- Report any posts that you feel should be brought to our attention.
- Please no shitposting or blogspam.
- No Referral Linking.
- Keep piracy discussion off of this community
founded 1 year ago
MODERATORS
8 lanes just refers that it has 8 lanes directly on card.
That you can connect 2 cables breaking out to 8 ports without the need for an expander.
The expander works similar to a network switch, the cables back to p408i-a is its uplink.
With 2 cables it aggregates the 8lanes to 8x 12gbit and those 96gbit is shared by the devices on the expander.
In the typical dl380 the expander would have 2 cables to each of the 3 front cages + have 2 spare ports for any drives you have in rear of server.
With a maxed out 30x 2.5" front+back server they share the 8 lanes to server.
You can even add another expander to the expander if you want, the card supports 200+ drives if you keep throwing expanders at it.
Thank you, that clears up alot.
So basically I have 3 front cages, each connected with 2 ports, as you said (DL380 Gen10). The expander has 9 ports, so 1 is free to use.
I'd like to connect a tape drive to it. It is using Mini-SAS, while the expander is Slimline-SAS. I found a converter, which uses a PCIe-Bracket (without the port, just passively converts), so from what I understood I should be able to convert Mini-SAS->Slimline-SAS and then just connect it with a slimine->slimline SAS cable to the expander?
How does the speed work - if it is like a switch the bandwidth would only suffer if the Tape is actively using the link? Or will it always decrease because the port is connected?
You can put a tape drive on the last port like you describe.
Nothing on the expander will suffer unless the full 96gbit link to raid card is saturated and it has to start throtteling stuff.
if you have something 4-8x cache SSDs with high load they would normally go in one cage and that cage gets its own controller.
To not risk saturating the link from expander and impacting performance + avoid the tiny latency expander adds.
Thank you again. I only have 10k 2,5" HDDs, so I guess I won't be close to saturating it. That really helps!