Very low write speed on cMP 5,1 (Samsung EVO 950)

[trchern]

I swapped my MBP 2012 2.5 SSD (which is Samsung 950 EVO) directly to my cMP 5,1. This drive is fast on my MBP, the write/read speed can go up to 500mb/s. However, when I tested in my cMP 5,1, the write speed is just around 25mb/s and read is around 250 mb/s. I know that the cMP is SATA2 which can not reach to the max performance of this SSD, but it is really too slow.

Maybe using SATA to PCIE adaptor is the way to go...

 

[tripmusic]

I had an OWC Mercury 3G running in the optical bay of a MP 5,1 and although I never tested the write speed, it ran fine to me. I'm thinking about getting a PCIE adapter myself to use with a faster SSD.

 

[AidenShaw]

I swapped my MBP 2012 2.5 SSD (which is Samsung 950 EVO) directly to my cMP 5,1. This drive is fast on my MBP, the write/read speed can go up to 500mb/s. However, when I tested in my cMP 5,1, the write speed is just around 25mb/s and read is around 250 mb/s. I know that the cMP is SATA2 which can not reach to the max performance of this SSD, but it is really too slow.

Maybe using SATA to PCIE adaptor is the way to go...

Is TRIM enabled?

 

[Macschrauber]

Maybe spotlight is indexing ? Have you waited long enough before testing ?

 

[bsbeamer]

Had an very similar issue with Samsung EVO 840's and 850's in MacPro5,1 connected directly via SATA sleds (OWC blue ones) when the drives were formatted APFS. System drive was "upgraded" to APFS when 10.13 was installed. I really noticed an issue with one of the security updates in 10.13.2. Do not recall which one, but did post about it on this forum.

Fix for me: cloned drive to an external formatted with HFS+ (not APFS) with Carbon Copy Cloner, install that drive as system drive and all problems were fixed.

Worth checking which firmware you're running for the Samsung SSDs. There are firmware updates available. They are a pain to install on Mac.

 

[trchern]

OK, now my drive back to "normal" speed. Both write and read are around 250.

I think maybe I am too eager to get the speed test right after the SSA swap and something is working in the background, like spotlight indexing, so the system is slow.

Btw, someone mention about trim enabling. If I do that, the read/write speed will run even faster? I thought that 250mb/s is the bottle neck of SATA2.

 

[AidenShaw]

OK, now my drive back to "normal" speed. Both write and read are around 250.

I think maybe I am too eager to get the speed test right after the SSA swap and something is working in the background, like spotlight indexing, so the system is slow.

Btw, someone mention about trim enabling. If I do that, the read/write speed will run even faster? I thought that 250mb/s is the bottle neck of SATA2.

The is no reason not to enable TRIM with current drives, and many reasons to enable it.

If you want consistently fast writes, enable TRIM.

Or, leave TRIM off and leave half of your drive unpartitioned. Both will give you consistently fast writes.

 

[hfg]

You might also use Disk Utility to run the "First Aid" on your SSD. It will perform a forced trim on all unused blocks as part of the process and then the Trim you enable will keep it clean. There is also a Terminal command to force Trim on the SSD that can be found in one of the threads here ... I think it is (someone more familiar with it might chime in here):

You are partway there. Now command-s boot to single user mode and enter the command below.

Code:
fsck -fy
You should see a notice at the end of the run that says "trimming unused blocks".... that TRIMS the free space on the drive and should restore your write speeds.

 

[Squuiid]

Use Aja Lite system test instead of Blackmagic. It’s much more reliable in my experience.
Choose 5K Red and 16GB from the menu then run.

https://itunes.apple.com/us/app/aja-system-test-lite/id1092006274?mt=12