SAS Expanders? IBM M1015 to Intel RES2SV240 vs multiple M1015's?

[guitarlp]

If I understand this correctly, I can connect two cables from an Intel RES2SV240 to the IBM M1015 card. This will essentially expand the 8 ports from the M1015 card to 16 total using the SAS expander right?

 

Why would I want to do that, compared to say running two M1015's, or two SUPERMICRO AOC-SASLP-MV8's?

[BobPhoenix]

I have ONE cable going from my M1015 to my Intel RES2SV240.  This lets me run 24 drives off a single M1015.  20 at a slower access speed and 4 at full 6GBs speed.  For me that is what I want as it saves my PCIe slots for other cards in ESXi.  I have one M1015 on passthrough to unRAID VM (max 24 drives) and another M1015 on passthrough to a Windows 7 session (max 8 drives without another SAS expander).  So only two slots used for HBAs.  I use the other two slots on my X9SCM-F for HVR=2250 tuner cards also on passthrough to Windows 7 session for SageTV server to record from.

[guitarlp]

I have ONE cable going from my M1015 to my Intel RES2SV240.  This lets me run 24 drives off a single M1015.  20 at a slower access speed and 4 at full 6GBs speed.  For me that is what I want as it saves my PCIe slots for other cards in ESXi.  I have one M1015 on passthrough to unRAID VM (max 24 drives) and another M1015 on passthrough to a Windows 7 session (max 8 drives without another SAS expander).  So only two slots used for HBAs.  I use the other two slots on my X9SCM-F for HVR=2250 tuner cards also on passthrough to Windows 7 session for SageTV server to record from.

 

Gothcha... that's making sense now. So each of the ports on the M1015 allows for 4 SATA connections at the full 6GBs speed. If I Took those two ports and used the SAS card you're using, it would bring down each SATA connection to 3 GBs and give me 16 Sata connections total.

 

But the better option (if I only wanted 16 drives) is to use two M1015's since that would give me 16 6GBs ports). Then again... that's only a benefit if I'm using SSD's on all those ports (which I'm not). I guess I could go either way. 2 M1015's can give me 16 6GBs ports, and 1 M1015 with the RES2SV240 would give me 16 3GBs ports, or 4 6GBs ports and 20 1.2GBs ports.

 

For my setup, I'm planning a 20 drive system this time around. So with 6 ports on the MOBO, I think I'd be better off with 2 M1015's so that I'll have 22 ports total (18 6GBs ports and 4 3GBs ports). That should also future proof me in case this server eventually starts hosting a bunch of SSD drives in the future.

 

Question though on ESXi. Since I'd like to run ESXi and start with unRAID and Windows Server 2012 (maybe Ubuntu Server to start with as well), is that going to give me any issues with the M1015's? I thought if these cards were passthrough cards I could assign any single drive connected to the M1015 to any OS I want through ESXi (for example, under one M1015 I'd have 5 drives for unRAID, 2 for Windows Server 2012, and 1 for Ubuntu)? But from what you're saying, it sounds like each M1015 needs to be assigned to a specific OS?

[BobPhoenix]

If you pass a card through to a VM it is exclusive to that VM as far as I know.  To do what you want here you would use an RDM mapped drive.  Check out Johnm's Atlas thread here.  If it is possible to share a card in passthrough mode it is beyond my knowledge.  Johnm might know or you could ask on the VMWare community forums for the definitive answer.

 

Also while slower the access speeds I see with only one cable appear to be greater than 1.2GB.  It is definitely comparable to SataI speeds but probably not SataII speeds.  Remember with PCIe 2.0 slots the transfer speeds can be higher that PCIe 1.0 with the same cards.  Also as you said you won't see much of a loss on a spinner but would be noticeable on SSDs.  My parity checks in my unRAID VMs might be a little slower than my SASLP-MV8's were but not by much.  So for me it is worth it for the added slot flexibility to use tuner cards.

 

I use RDM mapped drives for my WHSv1 VM on the same X9SCM-F this way I don't need to use a slot for a controller for it.