Blackmagic Speed Test results slowed down

[Black.Ghost]

When i got my 2012 Pro abut three weeks ago, it didn't have the little bar to hold my SSD in place, so I ordered one and installed it. The SSD didn't have the little screws in the side to help hold it in place, so I disconnected the battery and then the SSD in order to fit them. After putting everything back together, the speed test results for writing to the SSD are somewhat slower.

My first results were showing around 360MB/s write and 490 odd MB/s read. Now, they are showing anywhere between 145 and 200 or so. While determining the speed it does momentarily shoot up to around 270-280MB/s but doesn't stay there.

Any thoughts on why this might be the case? I have a new 500GB Crucial MX500 SSD in the machine.

Thanks

 

[treekram]

You should run Activity Monitor to see if there is any other disk activity going on before running Blackmagic. If you still get 145 write / 200 read, that's slow - I have a 250GB MX500 and when running it externally, I see the figures you did initially.

Since you have been doing de-installing and installing disks, it may have affected the HDD cable. If you don't know if the cable has been replaced recently, you should assume it's old and these cables have known problems as they age. You can try booting the SSD externally and see what kind of results you get. If you get the higher speeds, to me, the most likely cause would be the cable.

 

[iMacDragon]

Is trim enabled properly? this sounds like ssd that is in need of garbage collection.

 

[mbosse]

Is trim enabled properly? this sounds like ssd that is in need of garbage collection.

This I think is likely the cause for your slowdown. Enable TRIM, and you should be back fine.

Magnus

 

[treekram]

TRIM would not affect read performance but the OP has both degraded write and read performance according to Blackmagic.

 

[cynics]

Do an SMC reset if you haven't already. Disconnecting the battery can cause things to get wonky.

If you don't see an improvement boot into recover mode, go into disk utility in recovery mode and run first aid. You might have to mount the drive which can be done from disk utility. Disk Utility can then run First Aid and unmount the drive to check it and run maintenance without it being live.

Reboot normally and retest.

 

[mbosse]

TRIM would not affect read performance but the OP has both degraded write and read performance according to Blackmagic.

My experience is different:

I recently got a MBP from 2012 with a Samsung 840 Pro 512GB, where TRIM was not yet enabled. The read, but particularly the write speeds were abysmal:

I turned on TRIM and within a few minutes the readouts dramatically bettered - for both write and read:

Fast forward 30min, the practically to be expected factory values were restored

So, TRIM is clearly useful (it depends on the SSD type, not all brands/types react so positively to it).

Best,
Magnus

 

[Black.Ghost]

Thanks all.

I don't have the kit to be able to boot it externally, but it does seem to have happened since i removed and reinserted the SSD so it could well be the cable. I did change the destination drive to iCloud before hand (have deleted, and reinstalled BlackMagic to get the default though) and still doing the same.

TRIM has been enabled, but I will do the SMC reset and let you know. It's really frustrating.

 

[treekram]

My experience is different:

I recently got a MBP from 2012 with a Samsung 840 Pro 512GB, where TRIM was not yet enabled. The read, but particularly the write speeds were abysmal:

View attachment 832065

I turned on TRIM and within a few minutes the readouts dramatically bettered - for both write and read:

View attachment 832066

Fast forward 30min, the practically to be expected factory values were restored

View attachment 832068

So, TRIM is clearly useful (it depends on the SSD type, not all brands/types react so positively to it).

Best,
Magnus

The 840 Pro is an older SSD (introduced in Fall, 2012). Something extreme is going on with the drive as 24 MB/sec write is the performance one would expect from a HDD going bad. You can also see that whatever is going on affects the write performance much more than the read. For the OP the degradation affected write and read more equally.

But based on what you've presented, in the future I would say that for current name-brand SSD's, TRIM is unlikely to affect read speeds and is unlikely to be the problem if you experience consistent degradation between write and read. If someone comes up with a current name-brand SSD that exhibits the same behavior, I can be convinced otherwise (but please don't use a DRAM-less or a QLC SSD).
[doublepost=1555272492][/doublepost]

Thanks all.

I don't have the kit to be able to boot it externally, but it does seem to have happened since i removed and reinserted the SSD so it could well be the cable. I did change the destination drive to iCloud before hand (have deleted, and reinstalled BlackMagic to get the default though) and still doing the same.

TRIM has been enabled, but I will do the SMC reset and let you know. It's really frustrating.

One additional easy thing to try is running in safe mode to see if any background 3rd-party software is affecting the performance.
https://support.apple.com/en-us/HT201262