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I have old plastic white MacBook 13'' 2007 mid late.

In previous year I have bought SSD and replaced old one (HDD).

Everything was Ok, but in last month i started seen how sometime OS become stuck for one-two second, and then everything is ok.

Today I have download

Blackmagic Disk Speed Test

And it shows me good speed, but only at once. Seems to me it is testing my drive in cycle. It trying to write then read, then repeat cycle. So in first try it shows nice digits as a result, but then "write" (and only write) numbers become lower and lower, and fixing about 10 Mb/s. Is it mean that something non good with my SSD drive?

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3 Answers

mapasov pointed this link out for me to enable TRIM if you're using Lion http://digitaldj.net/2011/07/21/trim-enabler-for-lion/

It means that your system will handle TRIM as if it were a native Apple SSD, and that you shouldn't get the problem you're facing after the system has had time to manage it

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I agree. Probably a slow internal garbage collection is causing the problem. –  mspasov Jul 7 '12 at 12:54
    
Based on what i have found i don't need trim to enable. I have GC. My SSD is Crucial C300-CTFDDAC128MAG. I made firmware upgrade few motnh ago now it is 7th version, previously I have no such problems (with 6th firmware version), and I have about 40Gb free space yet –  x00xer Jul 8 '12 at 8:23
    
GC is managed by the SSD controller and does a similar thing to TRIM, but it's not the same. GC will wait until blocks are needed before it resets them in most cases as most systems don't idle long enough for it effectively work in the background. TRIM actively resets blocks when no longer needed so that you don't face performance issues. OS support for TRIM will give you better performance. Google for garbage collection vs trim if you need further evidence for this. –  AlanJC Jul 9 '12 at 14:32
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As AlanJC mentioned try Trim Enabler. Also its very important to check that you are running latest firmware on your SSD. You can see that under: About this Mac>More Info> System Report>Serial-ATA : Select the SSD and firmware version is listed as Revision. Get that and check if its latest for your SSD.

If you need to update it, there will be clear instructions along with the update on how to run it.

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I have latest version ;( and seems to me not only I have such problems :( Can it be becasue I have old Sata 1,5 Gb/s ? and my SSD can work with SATA III ? –  x00xer Jul 8 '12 at 8:38
    
SATA I is still compatible you just get lower speeds. Although the speed you describe is too low. Maybe try with customer support. p.s: with SATA II (and III) my crucial M4 was getting 170 mn write. Not sure how much lower you get with SATA I but shouldn't be more than half. –  latusaki Jul 8 '12 at 12:29
    
after first start I have this picture o7.no/LYahXM after 3rd, 4th run, write speed become about 20-30 Mb/s –  x00xer Jul 9 '12 at 11:49
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Sounds like you are writing data to it faster than the controller's garbage collection can create free pages for writing. Make sure you have plenty of free space and leave the system idling to make sure the controller has time to run GC.

You can read about the underlying technical details elsewhere but, as a general rule, OS X is sensitive to GC since TRIM is only enabled on Apple SSD's.

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