SSDs get defragged?


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I thought it was pretty clear.  I am going to try to summarise my understanding of the article.

 

The crux was a large MFT (i.e. one with lots of items on it) is bad.  There are limitations on how big it can grow (as with anything in the world of computing), and it is very bad when you go over these limitations.

 

From an algorithm point of view, applying all the same rules that would be applied when defragging a spinning disk when defragging an SSD would be harmful

 

With a spinning disk, you reduce the number of fragments so the MFT is kept as small as possible, this combined with making sure the fragments are close together improves disk performance by reducing seek time.

 

WIth an SSD, keeping the number of fragments small is important but keeping the fragments close together actually has no benefit.  In fact it is bad because you are moving stuff around reducing the life of the SSD, with no benefit.

 

Now it's quite possible that I have completely misread it, in which case please ignore this in its entirety.

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Ummm don't defrag because it will put a ton of wear on your SSD drive! who in the hell told you it was ok?

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I am curious to know how it works though. How can it "defrag" and guarantee that data is sequential on the drive? As I said, I thought with wear leveling, data is not always sequential - this having a fragmented drive (data scattered around) is good.

Write_Amplification_on_SSD.pngtech5-1.jpg

trim_full.jpg

http://en.wikipedia.org/wiki/Trim_%28computing%29  <---Good reading.

http://en.wikipedia.org/wiki/Wear_leveling   <---more

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Like I said. I know how wear leveling works. Global wear leveling looks like it has data scattered around to me. I do not know how defragging an SSD works. How does it make the data sequential? Why can't we do the same thing and write zeroes on the drive and wipe it?

Like I said, that article is not very good. I do not think windows actually defrags the drive. How can it? If it has to move data around, how can it guarantee it is sequential?

Isn't that the entire reason that everybody says not to defrag SSDs (because of wear leveling)? I know how wear leveling works, so how can Microsoft defrag SSDs?

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Like I said. I know how wear leveling works. Global wear leveling looks like it has data scattered around to me. I do not know how defragging an SSD works. How does it make the data sequential? Why can't we do the same thing and write zeroes on the drive and wipe it?

Like I said, that article is not very good. I do not think windows actually defrags the drive. How can it? If it has to move data around, how can it guarantee it is sequential?

Isn't that the entire reason that everybody says not to defrag SSDs (because of wear leveling)? I know how wear leveling works, so how can Microsoft defrag SSDs?

 

 

 

https://www.neowin.net/forum/topic/1242350-ssds-get-defragged/?view=findpost&p=596707846

 

http://www.outsidethebox.ms/why-windows-8-defragments-your-ssd-and-how-you-can-avoid-this/  <---This is good but read the whole article.

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I thought I read that you're not supposed to defrag SSD's. I've been using my current build for several years and it's still running lightning fast without any defragging. Samsung's software for optimizing performance is terrific though.

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I thought I read that you're not supposed to defrag SSD's. I've been using my current build for several years and it's still running lightning fast without any defragging. Samsung's software for optimizing performance is terrific though.

That was my understanding too. But why does Microsoft do it? Why doesn't Apple or Linux do it if it is required?

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That was my understanding too. But why does Microsoft do it? Why doesn't Apple or Linux do it if it is required?

It does not sound like a problem with SSDs but a problem with the filesystem, so perhaps it is a limitation of NTFS?

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 How can it guarantee data is sequential?

Due to multiple channels and buffers data on an SSD does not need to be sequential while still providing optimum performance. SSD's can read multiple fragments at once.The best thing to do with an SSD is to occasionally check for firmware updates that improve performance and run TRIM weekly. 

Source: https://www.usenix.org/legacy/event/hotstorage11/tech/final_files/Yoo.pdf

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Due to multiple channels and buffers data on an SSD does not need to be sequential while still providing optimum performance. SSD's can read multiple fragments at once.The best thing to do with an SSD is to occasionally check for firmware updates that improve performance and run TRIM weekly.

Source: https://www.usenix.org/legacy/event/hotstorage11/tech/final_files/Yoo.pdf

Yes that was my entire argument regarding wear leveling. Data is in a sense fragmented because it is not sequential. Why do we defrag mechanical hard drives? When a hard drive is fragmented, data is not sequential right? Therefore, we actually want a fragmented SSD.

So I was right all along, the drive itself does not get defragged, just the file system. The article should not say it defrags the SSD because it does not. It defrags the file system. Data can be anywhere on an SSD, it doesn't need to be sequential so it doesn't need to get defragged.

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