SSD Alignment

[nskii]

Hi

So I've been having slow speeds on SSD Samsung 840 250GB in macbook pro 13 mid 2012. Black magic shows around 120MB read and 30MB write. Booting time i believe is decent, around 22sec. Trim is enabled with TRIM Enabler. SSD was swapped with a stock 500GB HDD. The OS installed is 10.10.1

I've done some digging about ssd alignment with a hope this would improve my speeds. I used the command sudo gdisk /dev/diskX to check blocks. This is what i get:

GPT fdisk (gdisk) version 0.8.10

Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
NOTE: Write test failed with error number 16. It will be impossible to save
changes to this disk's partition table!

Partition table scan:
MBR: not present
BSD: not present
APM: not present
GPT: not present

Creating new GPT entries.

Command (? for help):

I am unfamiliar with terminal and its command lines. This is the article i've used:
https://forums.macrumors.com/posts/16842880/

Any help would be much appreciated!
Best regards, Nino

 

[Apple_Robert]

Is your SSD up to date with the latest firmware? That is the first thing I would check.

 

[nskii]

Yes, I've connected it with a PC and updated the firmware with the Samsung software. The speeds on a PC are much higher. Around 350MBs both write and read.

 

[cruisin]

This is a guess but if you go to Disk Utility and click verify permissions and verify disk, does it show any errors? Might help.

 

[yjchua95]

Yes, I've connected it with a PC and updated the firmware with the Samsung software. The speeds on a PC are much higher. Around 350MBs both write and read.

Can you check under System Information → SATA/SATA Express and see whether it's connected on a 6 Gigabit link or not?

I've provided an attachment from my own MBP as a reference.

 

[nskii]

Its a 6gigabit link. Im not sure about Disk permissions but volume verification seems to be ok. (both reports in attachments)

 

[glenthompson]

Some people have had problems with the SATA cable. It may have become damaged in the SSD installation.

 

[yjchua95]

Its a 6gigabit link. Im not sure about Disk permissions but volume verification seems to be ok. (both reports in attachments)

It doesn't say 6 Gigabit anywhere in the screenshot.

 

[simonsi]

If you are getting 350MB speeds in a PC then I don't believe there is much wrong with your SSD hardware, if your firmware is up to date then that pretty much rules that out.

Alignment? That post you link to is nearly 5yrs old, I'd not expect any such issues now.

Did you re-partition to test on the Win machines as you show 250GB used on a GUID partition under OSX?

Please double-check it is showing "negotiated at 6Gb" speed in system info, you screenshot is scrolled down from where it is shown.

MBP drive cable is a definite possibility, to rule it out you can temp connect the SSD on the Optical drive cable to test, see what speed it negotiates and tests at there.

 

[nskii]

So sorry, it scrolled down when I screen capped it.

I tested the NTFS re-partitioned drive on Windows.

Thats a good idea, I'll swap it with an optical drive. Hopefully its not too risky to take out an optical drive bay.

I checked the ifixit guide and it seems pretty risky with necessary removing a bunch of connectors. Should i take it to the service instead?

 

[nskii]

I just tested SSD speeds with AJA system test and this is what i got... I'm confussed

 

[cruisin]

Is the SSD empty now? If it was filled up last time your reading could be low. I tried both Blackmagic and AJA and they are somewhat close in results but AJA is a bit higher.

Maybe the reformat fixed something as you went to Windows and back?

The only thing that I can think of is that you did a speed test right when you first installed OSX and Spotlight was still indexing everything. So the SSD was in use when you did the test. Retry the test and see if it has improved.

Here is what I get:

 

[nskii]

Reformat was done more than a month ago. I just tested the black magics benchmark and it shows much better results now aswell. Im not sure why is that so, I basicaly haven't done anything lol. Writes are still somehow low for an SSD but much higher than before. SSD is right at 50% of its capacity.

@Cruisin those PCI-E SSD speeds look silly fast tho lol.

I hope speeds stay this way! I am doing a memory upgrade soon to 8GB and didn't want to purchase until i get to the bottom of the SSD speed issue.

BTW which DDR3 1600MHZ do you guys recommend?