Low SSD Write Speed w/ Samsung 850 Evo

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Level 1

4 points

Low SSD Write Speed w/ Samsung 850 Evo

Hey Folks,

I have a 15 inch Macbook Pro, Mid 2010, that I recently upgraded to an SSD drive. I used the Samsung 850 Evo to upgrade the device and am now seeing write speeds that I believe are less than what should be normal for my machine given an SSD upgrade. My machine does have a SATA II connector, which I know will limit the read and write speeds somewhat, but I think something more than that is happening here.

Using BlackMagic, my new drive is able to achieve a write speed of about 126 MB/s and a read speed of 265 MB/s. The 850 eve itself is advertised above 500 MB/s on both read and write using a SATA III connector, so I'm assuming I can reasonably expect those speeds to be halved when using a SATA II connector. However, the write speed just seems to be too slow even for SATA II.

So, I'm wondering if there might be something wrong with the drive? I'm running OS X 10.11 (El Cap GM) with 8 GB RAM. Looking at disk utility, nothing seems out of the ordinary.

I'm having my doubts about the 850 Evo. The samsung website shows it as being really Windows centric and I'm not able to find any software that's isn't in .exe form. Is there a way to update the firmware? Have I made an error in choosing this brand? Might you know what could be causing the low write speeds?

Any help is appreciated.

Thanks!

MacBook Pro, null

Posted on Sep 11, 2015 9:49 AM

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Answer 1

Best reply

Grant Bennet-Alder

Level 10

126,817 points

Sep 12, 2015 6:15 PM in response to Ken2950

Have you enabled TRIM?

If you do not know what TRIM is, this article will give you a quick start:

https://en.wikipedia.org/wiki/Trim_(computing)

.

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Answer 2

OGELTHORPE

Level 9

57,305 points

Sep 11, 2015 10:33 AM in response to Ken2950

You are in a difficult situation. Now you know that Samsung does not mention Mac compatibility on their web site. You could give them a call and see if they can give you some guidance, but do not count on that.

There have been a number of problems (and successes) with Samsung SSDs posted on these forums, but you have added an additional complicating factor, El Capitan. This may or may not have an effect, but since it is in beta status, it is not likely that anyone here can assist you with that aspect.

The best advice I can offer is to see if you can rid the MBP of El Capitan and install the prior OSX. You may or may not be able to do that. If successful, try to reinstall the SSD.

Another limiting factor has been found is the internal SATA connection cable. By replacing it, satisfactory performance has been achieved. I do not guarantee that will solve the problem but it has for others. I do not know of any way to test if that is the problem.

Ciao.

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Answer 3

Ken2950 Author

Level 1

4 points

Sep 12, 2015 6:24 PM in response to Ken2950

Grant and Oglethorpe,

Thank you for your replies.

After doing much digging around in different forums and such, I uncovered the reason behind the slow write speeds...and it was a painfully simple and overlooked mistake on my part.

When I setup El Cap from a clean install, it asked me if I wanted to turn on FileVault2 - to which I selected "yes". Naively, I thought that was all there was to the process, but as it turns out, to encrypt the SSD, FileVault has to slowly scan the entire disk and apply the encryption. It was doing this for 2 days. During the time it was working, my write speeds were abysmal. As soon as FileVault finished encrypting the disk, the write speed shot back up to 250-260 Mb/s which is what I expect with a SATA II connector.

For anyone else that has a similar issue, check to see if your disk is being encrypted by FileVault by going to: >System Prefs>Security and Privacy>FileVault. If it is being encrypted, it'll show a "progress bar" towards the bottom of the file vault window.

Moral of the story: Encryption is a slow (but useful) process. Let it finish an your SSD should be good to go afterwards.

Cheers!

P.S. El Cap is running great on my Macbook now. Everything is very speedy and I'm convinced that my battery life has improved with the new OS and the SSD! Love it.

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Answer 4

mhazani

Level 1

4 points

Feb 14, 2016 11:05 AM in response to Ken2950

Came here with the exact same question after a fresh install of El Cap, and your discovery is exactly what's going on with mine! (hopefully that's ALL that's wrong:)

With a brand new SSD the speeds are far worse than before all my upgrades, but I'm going to put my faith in Apple God and your findings, and let it finish encrypting before jumping to conclusions;). Just wanted to say - thanks for easing my concerns!

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Answer 5

Feb 14, 2016 2:45 PM in response to mhazani

The AES instruction set extensions to the Intel processor family were introduced after about 2009, in all i5 and 17 processors, and in Westmere and later Xeon processors (all 2010 Mac Pro 5,1 models except the four-core).

These built-in instructions make decrypting your individual items for actual use really quick.

There is nothing you can do but wait for that l-o-n-g encryption cycle.

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Answer 6

mhazani

Level 1

4 points

Feb 14, 2016 2:51 PM in response to Grant Bennet-Alder

tbh it took under two hours - probably helped that the SSD had nothing on it but OSX. Not sure why the huge deifference between OP's two days and my two hours, but counting my blessings nonetheless!

PS - can confirm, post-encryption SSD is now blazing fast!

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