The ServeRAID M1015 SAS/SATA Controller - how many physical SATA drives I can connect

Vladimir Buzalka
Vladimir Buzalka used Ask the Experts™
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Dear Experts

I have a question related to controller M1015. I want to use it in IT mode for Unraid server.

In specification I can read this:
The ServeRAID M1015 SAS/SATA Controller has the following specifications:

Eight internal 6 Gbps SAS/SATA ports
Supports SAS and SATA drives (but not in the same RAID volume)
Two Mini-SAS internal connectors (SFF-8087)
6 Gbps throughput per port
LSI SAS2008 6 Gbps RAID on Chip (ROC) controller
x8 PCI Express 2.0 host interface
Supports RAID levels 0, 1, 10 (RAID levels 5 and 50 with optional ServeRAID M1000 Series Advanced Feature Key)
Connects to up to 16 SAS or SATA drives
Supports up to 16 logical volumes
Supports LUN sizes up to 64 TB
Configurable stripe size up to 64 KB
Compliant with Disk Data Format (DDF) configuration on disk (COD)
S.M.A.R.T. support

What I do not understand is - does this controller allows to connect 16 physical SATA drives? If yes why it reports only 8 internal ports?

many thanks for your advice

Vladimir
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John TsioumprisSoftware & Systems Engineer

Commented:
Simply by reading the specs it seems correct
8 SAS/SATA ports  & 2x4 SATA drives
Software & Systems Engineer
Commented:
EDIT : i went to product page...No its 8 disks..at least i cannot see any extra ports ...you get only the 2 Mini-SAS internal connectors (SFF-8087)
John TsioumprisSoftware & Systems Engineer

Commented:
EDIT again sorry : On this product leaflet it states 32 drives...how they are connected beats me
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Top Expert 2014
Commented:
You can have SAS expanders that let you connect more physical disks than you have ports. In the case if a controller the expanders would normally be on the backplane of the disk cages.

Here's an example of a SAS expander, in this case two cables go to the controller and then the other 7 ports go to drive cages. Yhe PCIe slot is just for power, no data lines on it.

https://intelligentservers.co.uk/components/hpe-12gb-sas-expander-card-with-cables-for-dl380-gen9-727250-b21-761879-001/?gclid=CjwKCAjwkqPrBRA3EiwAKdtwk0scLxhce7bd1818iHbv2anhFC3QAZ0b4ffEK2ut_ZVH8OyIF2ltlBoCE7gQAvD_BwE
John TsioumprisSoftware & Systems Engineer

Commented:
Is it just me or i see the whole SAS expander is an overkill ...usefull but ?
From what i "see" 8 drives should be the "usual" scenario.
Top Expert 2014

Commented:
Here's an IBM backplane with SAS expander on it, https://forums.servethehome.com/index.php?threads/ibm-x3650-m4-add-on-sas-backplane-power-woes.17531/ . SAS cables go in one side and daisy-chain out on the other side. 8 disk slots are not seen. the expander chip is under the heatsink.

Author

Commented:
Thanks for all your comments, so now we know that it is doable to connect 16 or 32 drives to controller.

But very clearly we can conclude that price for expender is like price for low entry server :-) and for sure many times more compared to controller card itself.

So my solution would be to buy simply 2 M1015 cards (one is for 40 USD) and I can connect "natively" 16 drives. As I need 12 I am OK with this.

Do you agree with me or there is some "but" hidden in this solution?

many thanks

V
Top Expert 2014

Commented:
Yes John, generally overkill for internal disks as it's cheaper to use two controllers but then you can't have one big array.  For external disk shelves then expanders are essential as you may daisy-chain 100 disks on one channel. Don't think anyone makes an external disk shelf without an expander or two in it.

Author

Commented:
many thanks all

Author

Commented:
Clearly explained.
John TsioumprisSoftware & Systems Engineer

Commented:
I would also walk the same path...and if its seems like a "con" that you don't get the BIG array ... ...lets say : don't put all your eggs in one basket

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