I currently have a 24 bay SM case that has individual SAS/SATA connections for each bay. I'm running 3 M1015 HBAs to connect to all the drives. Recently I acquired 24 3TB SATA drives and I'm looking at a 36 bay case to put them in and transplant the 12 2TB drives in my existing case. The 36 bay cases I've seen all have expander backplanes. I don't have any experience with expanders. The system is home storage, lots of media files and also backend storage for a VM cluster. I have an Intel s3500 SSD as SLOG. Will there likely be a performance penalty using expanders? Are there any other issues using expanders that I should be aware of?
![[H]ard|Forum](/styles/hardforum/xenforo/logo_dark.png){kind=logo}
Supermicro Backplanes - Expanders vs Direct Connections
- Thread starter Ripley
- Start date
When it comes to supermicro chassis with SAS1 expanders there is a known issue with drives larger than or equal to 3TB. To alleviate this ensure that either the backplane uses sata connectors or that it is SAS2. The easiest way to figure this out is to check the parts list on any chassis you are interested in, and make sure it uses a SAS2 backplane.
Good (BPN-SAS2-836EL1): http://www.supermicro.com/products/chassis/3U/836/SC836BHE16-R1K28.cfm?parts=SHOW
Bad (BPN-SAS-836EL1): http://www.supermicro.com/products/chassis/3U/836/SC836E1-R800.cfm
I thought you could only dual link with SAS drives? I will be using SATA drives.
There are dual port enterprise SATA disks, but if you do get that kind of budget, get SAS.
Running two SFF-8087 cables between your HBA and SAS expander is not limited to SAS disks. Keep in mind that a single SFF-8087 cable already carries 4 lanes, so you're just doubling it to 8. You're confusing things with dual expander backplanes where they use multiple ports on the disk side.
With just hard drives you won't really see any performance hit so long as you're running both cables. Also, the Supermicro 847 is available in a version without the SAS expander backplanes. I'd still recommend the SAS2 expander backplanes (as mentioned earlier) just because it makes things so much simpler/cleaner (ie not running 9 thick cables).
With just hard drives you won't really see any performance hit so long as you're running both cables. Also, the Supermicro 847 is available in a version without the SAS expander backplanes. I'd still recommend the SAS2 expander backplanes (as mentioned earlier) just because it makes things so much simpler/cleaner (ie not running 9 thick cables).
Dual-Link is not Dual-Port. Don't get them mixed up.
Dual-Link is the ability of the SAS expander to spread traffic over a second x4 link (i.e., 8087 cable). LSI-based expanders like the SM SAS2-EL1 support this. LSI SAS HBAs like the M1015s you are using also support this.
Dual-port is the ability to have more than one host access a single drive. When using expanders this usually implies using a "dual expander" like SuperMicro's SAS2-EL2.
Dual-Link is the ability of the SAS expander to spread traffic over a second x4 link (i.e., 8087 cable). LSI-based expanders like the SM SAS2-EL1 support this. LSI SAS HBAs like the M1015s you are using also support this.
Dual-port is the ability to have more than one host access a single drive. When using expanders this usually implies using a "dual expander" like SuperMicro's SAS2-EL2.
BlueFox/PigLover - Thanks for clearing that up for me. One more question, do I still need multiple HBAs with an expander backplane?
I had to email the seller to and provide them info on how to locate the backplane model. Its not one of the two mentioned in this thread already. Its a BPN-SAS-846A. I've googled but can't find any info on whether that backplane has issues with drives at or above 3TBs. Anyone know?
I had to email the seller to and provide them info on how to locate the backplane model. Its not one of the two mentioned in this thread already. Its a BPN-SAS-846A. I've googled but can't find any info on whether that backplane has issues with drives at or above 3TBs. Anyone know?
No, you'd only need a single HBA when using an expander. That backplane is a non expander one. Backplane naming goes as follows (last letters after the chassis model number which is 846 in this case):
TQ = individual SATA ports
A = individual SFF-8087 ports
EL1 = single SAS expander
EL2 = dual SAS expander (only beneficial over EL1 when you have SAS drives)
That one should have no issues with large drives since the backplane has no logic and is just directly passing the disks through (so no different than a cable).
TQ = individual SATA ports
A = individual SFF-8087 ports
EL1 = single SAS expander
EL2 = dual SAS expander (only beneficial over EL1 when you have SAS drives)
That one should have no issues with large drives since the backplane has no logic and is just directly passing the disks through (so no different than a cable).
I believe you will run into issues with that backplane.
I found a couple posts on various sites where people were using the backplane with 4TB drives. Can you elaborate on why you think I would have problems?
I would not touch any SAS (i.e., SAS-1) expander backplane. Too many bugs. SAS2 backplanes are fine and starting to become reasonably priced on the used (ebay) market now that SM is shipping SAS3 backplanes in quantity.
That's great info Bluefox, thanks. If I can get it for the right price I'm going to pick it. Now I just need to figure out how I'm going to connect the extra 12 drives. It seems like an expander is my best bet, probably the Intel one, instead of 2 more M1015s.
