Learned new things about SSDs and fragmentation

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PurpleGurl
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Learned new things about SSDs and fragmentation

Post by PurpleGurl »

I've always thought it was bad to defragment SSDs. Yes, it is bad practice because of the type of media (at least until 3D x-point memory and other nonvolatile memory becomes more widely available). Yet, due to file system limitations, it is possible for the file to be too fragmented in the tables for it to work properly, even though the reads are not impacted. There just comes a point where the metadata about the file placement will break down. And many fragments means more file location data that Windows must process. So you can get performance hits from fragmentation on an SSD drive, just not as much.

Then there is how newer Windows versions handles TRIM. If there are too many Trim requests in the queue, the OS will start dropping some. So that is why the modern Windows versions use a Retrim command.

http://www.hanselman.com/blog/TheRealAn ... urSSD.aspx
erkinalp
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Re: Learned new things about SSDs and fragmentation

Post by erkinalp »

There is a queued trim command with a disk-managed queue.
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PurpleGurl
Posts: 1790
Joined: Fri Aug 07, 2009 5:11 am
Location: USA

Re: Learned new things about SSDs and fragmentation

Post by PurpleGurl »

I just never thought that maybe a file could be too fragmented to extend. With moderate fragmentation, you'd not notice it on a SSD drive. However, performance isn't the only reason to defragment. If a file is in thousands of fragments, it might just overwhelm the NTFS system. I can only think of 2 situations where that would naturally occur. One is a file like a log that keeps getting extended without being deleted. The other is that the entire disk is severely fragmented and someone writes a huge file. And if it is bad enough, the operation will fail.
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