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SAS controller negotiated speed slow

D

DWZ

n00b
Joined
May 10, 2015
Messages
1
Hi there,

First up, sorry if this is a stupid question, but I'm new to the storage game. I'm having a trouble whereby my SATA disks in my storage array are negotiating a speed slower than the drive is capable for reasons I'm not understanding.

My setup is that I've got an IBM ServeRAID M1115 card, a HP 6 Gbps SAS Expender Card 24-Port (468405-001), and a Norco RPC-4224 server case.

As I understand it, each of these three components support 6 Gbps SATA disks. In reality, it seems to be randomly selecting a negotiated speed of either 3.0 Gbps and 1.5 Gbps on each disk. 3.0 is fine by me, but what's causing me a problem is that a large number of the drives are being negotiated down to 1.5.

My setup is as follows:

MegaRaid M1115 - SAS Port 1: -- uplink to SAS expander --
MegaRaid M1115 - SAS Port 2: -- SAS port not connected --

HP SAS Extender - SAS Port 1: -- uplink to MegaRaid --

HP SAS Extender - SAS Port 2 - SATA Disk 1: 3TB HDD, Drive Speed 6.0, Negotiated Speed: 3.0
HP SAS Extender - SAS Port 2 - SATA Disk 2: 3TB HDD, Drive Speed 6.0, Negotiated Speed: 1.5
HP SAS Extender - SAS Port 2 - SATA Disk 3: 3TB HDD, Drive Speed 6.0, Negotiated Speed: 1.5
HP SAS Extender - SAS Port 2 - SATA Disk 4: 3TB HDD, Drive Speed 6.0, Negotiated Speed: 1.5

HP SAS Extender - SAS Port 3 - SATA Disk 1: 3TB HDD, Drive Speed 6.0, Negotiated Speed: 1.5
HP SAS Extender - SAS Port 3 - SATA Disk 2: 3TB HDD, Drive Speed 6.0, Negotiated Speed: 1.5
HP SAS Extender - SAS Port 3 - SATA Disk 3: 60GB SSD, Drive Speed 3.0, Negotiated Speed: 3.0
HP SAS Extender - SAS Port 3 - SATA Disk 4: 500GB HDD, Drive Speed 3.0, Negotiated Speed: 3.0

HP SAS Extender - SAS Port 4 - SATA Disk 1: 300GB HDD, Drive Speed 3.0, Negotiated Speed: 3.0
HP SAS Extender - SAS Port 4 - SATA Disk 2: 60GB SSD, Drive Speed 3.0, Negotiated Speed: 3.0
HP SAS Extender - SAS Port 4 - SATA Disk 3: -- no drive installed --
HP SAS Extender - SAS Port 4 - SATA Disk 4: -- no drive installed --

HP SAS Extender - SAS Port 5 - SATA Disk 1: -- no drive installed --
HP SAS Extender - SAS Port 5 - SATA Disk 2: -- no drive installed --
HP SAS Extender - SAS Port 5 - SATA Disk 3: -- no drive installed --
HP SAS Extender - SAS Port 5 - SATA Disk 4: -- no drive installed --

HP SAS Extender - SAS Port 6: -- SAS port not connected --
HP SAS Extender - SAS Port 7: -- SAS port not connected --
HP SAS Extender - SAS Port 8: -- SAS port not connected --
HP SAS Extender - SAS Port 9: -- SAS port not connected --

All disks are operating in JBOD, no hardware RAID.

In terms of cabling, I've got a 1 meter SAS cable (SFF-8087 to SFF-8087) connected to a 'SFF-8087 to SFF-8088 adapter', connected to another 0.5m cable (SFF-8008 to SFF-8008) connecting the controller to the expander. The four cables going between the expander to the backplanes are all 0.5m in length.

I tried moving some of the 1.5 Gbps disks to other drive bays, in some it continued to negotiate at 1.5, but in other cases it negotiated up to 3.0 - so I'm wondering if the backplane or the SAS ports are oversubscribed or something. I'm also a little confused as to how much data can go across the uplink port between the controller and the expander before it causes a problem, and if 1.5m of cabling between them is too long.

Anyone got any thoughts on what the problem might be?
 
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