Send News. Want a reply? Read this. More in the FAQ.   News Forum - All Forums - Mobile - PDA - RSS Headlines  RSS Headlines   Twitter  Twitter
Customize
User Settings
Styles:
LAN Parties
Upcoming one-time events:

Regularly scheduled events

Morning Tech Bits

View
9 Replies. 1 pages. Viewing page 1.
< Newer [ 1 ] Older >

9. Re: Morning Tech Bits Dec 22, 2012, 09:52 Tom
 
I apologize for the caps lock, as well as the improper (but perhaps amusing) use of the word "perpetrating". This is a major pet peeve of mine and it drives me crazy that the issue has been swept under the rug by everyone: SSD manufacturers, OS vendors, tech reviewers, defrag software vendors, everyone! And none of them ever bother to explain what's really going on. They just say "oh well defrag is pointless on SSDs, doesn't do anything except wear out the flash, don't do it, don't pay any attention to that, it doesn't apply, you can pretend it doesn't exist".

You mentioned that Windows disables its defrag on SSDs. This is not a good thing. This is an irresponsible easy out for MS. Over time, filesystems will become more and more fragmented (NTFS is VERY prone to fragmentation) and this problem will absolutely contribute to the "Windows feels slower over time" problem. Not like they're strangers to that though. Just buy a new PC. Buy a new SSD. Format+reinstall. Everyone's happy, right?

Even though the problem is absolutely solvable, nobody in a position to do anything cares. This is a sad state of affairs.

If you're interested in understanding the truth, don't just take my word for it. Here are good starting points - note that even Wikipedia usually fails to cite sources for claims related to this point, and even sometimes contradicts itself on this point within the same article:
http://en.wikipedia.org/wiki/File_system_fragmentation
http://en.wikipedia.org/wiki/TRIM
http://en.wikipedia.org/wiki/Solid_state_drives

Also, here's a tool you can use to easily measure fragmentation and defragment on a file by file basis:
http://technet.microsoft.com/en-us/sysinternals/bb897428.aspx

I base my statements on a moderate understanding of how filesystems work (having implemented a simple one) as well as my direct observations. I have personally measured a 35% difference in time taken to read a downloaded file from an SSD whether it was in 150 fragments or 1, taking care to make sure the reads were not coming from the OS's disk cache. I encourage everyone to make their own direct observations, though I know it's not easy.
 
Reply Quote Edit Delete Report
 
8. Re: Morning Tech Bits Dec 21, 2012, 08:55 Verno
 
WRONG! Please stop perpetrating this myth. The truth is that filesystems on SSDs are just as prone to fragmentation as they are on traditional hard drives, and defragmentation has the same purpose on all drives: to eliminate fragmentation. The key differences with SSDs are that 1) the slowdown caused by fragmentation is not nearly as severe as it is with traditional hard drives (but it still exists!), and 2) there's a real wear cost to defragmentation. So things get a little complicated.

CAPSLOCK! I don't work with this stuff at a low level admittedly and some of what you said made sense but I've also read opposition conclusions on some sites so while I'm happy to learn new things, it helps if you cite some material instead of just asserting it. For example Windows actually disables its own internal defragmentation scheduler on drives it detects as SSDs and most benchmarks I've seen have concluded that fragmentation is a non-issue while using an SSD since the performance gain is minimal at best.

It it worth defragmenting a filesystem stored on an SSD? Usually not. Not because "there's no purpose in doing so" but because it's not worth it from a cost/benefit standpoint. The cost of defragmentation is that you cause physical wear due to the many erase/write cycles caused by the OS trying to make things contiguous again via rearranging blocks

That's actually been my understanding based on what I read already which is what I meant by "no purpose in doing so" instead of a rambling explanation that I didn't fully grasp. But thank you for explaining some of the particulars in general, the block level explanation cleared up a lot

This comment was edited on Dec 21, 2012, 09:03.
 
Avatar 51617
 
Playing: Divinity Original Sin, Destiny, Fire Emblem
Watching: Continuum, Star Trek TNG, Haunt
Reply Quote Edit Delete Report
 
7. Re: Morning Tech Bits Dec 20, 2012, 22:56 Jivaro
 
Verno, you damn perpetrator! Stop that!  
Reply Quote Edit Delete Report
 
6. Re: Morning Tech Bits Dec 20, 2012, 18:51 Tom
 
Verno wrote on Dec 20, 2012, 14:14:
DangerDog wrote on Dec 20, 2012, 14:05:
I thought I read that you shouldn't defrag SSD drives

That's correct, there's no purpose in doing so and it usually conflicts with the drives internal garbage collection.

WRONG! Please stop perpetrating this myth. The truth is that filesystems on SSDs are just as prone to fragmentation as they are on traditional hard drives, and defragmentation has the same purpose on all drives: to eliminate fragmentation. The key differences with SSDs are that 1) the slowdown caused by fragmentation is not nearly as severe as it is with traditional hard drives (but it still exists!), and 2) there's a real wear cost to defragmentation. So things get a little complicated.

SSDs are much faster at reading data scattered around different locations, since they don't have to move a drive head over the correct portion of a spinning disk. But even on SSDs there can still be a performance penalty imposed by the overhead of fragmentation. This can be a measurable and sometimes even very noticeable impact when files are split into hundreds or thousands of fragments. Extreme fragmentation happens more often than you might expect, especially if the volume is used a lot while nearly full, and fragmentation breeds fragmentation. When reading a heavily fragmented file, the OS can no longer issue relatively few large, regularly sized read requests. It has to instead issue a larger number of smaller, irregularly sized read requests. If you know anything about SSD performance and benchmarking, you know that SSDs perform better (sometimes DRASTICALLY better) at larger I/O sizes. Now, good modern SSDs may achieve a comparable throughout on many small I/O requests vs. relatively few large ones, but this is hardly guaranteed. Chances are, if you actually measure, you will find a significant performance difference between reading a heavily fragmented file from an SSD vs. reading an unfragmented file.

Please understand that fragmentation happens at the FILESYSTEM level. The SSD has no notion of filesystems. It's a block level storage device that makes many small blocks of storage available to the OS. The OS then makes this storage available via a filesystem. Therefore, any garbage collection or wear leveling done by the SSD is not happening at the filesystem level and has nothing to do with filesystem fragmentation. The only way the SSD is even remotely aware of the filesystem structure is via the TRIM command, which the OS uses to inform the SSD that data has been deleted. The SSD can then take this information into account when doing its own internal garbage collection and preemptive erasing of flash cells. This improves performance of future I/O operations and reduces unnecessary wear on the flash.

BOTTOM LINE:

It it worth defragmenting a filesystem stored on an SSD? Usually not. Not because "there's no purpose in doing so" but because it's not worth it from a cost/benefit standpoint. The cost of defragmentation is that you cause physical wear due to the many erase/write cycles caused by the OS trying to make things contiguous again via rearranging blocks, without the SSD understanding what's really going on. The benefit is improved performance, which may or may not be noticeable or significant depending on the situation.

In the future, it would be nice if OS and SSD manufacturers would make it possible for the OS to remap block addressing on the SSD in an intelligent, coordinated way. This would allow true defragmentation of the filesystem without wearing out the flash memory on the SSD. The SSD could then lazily rearrange data in flash as it sees fit in order to optimize future requests. But given how much trouble it was just to get TRIM (a relatively basic level of coordination between OS and SSD), and how readily the public buys these lies about the nature and effects of fragmentation, this may never happen.
 
Reply Quote Edit Delete Report
 
5. Re: Morning Tech Bits Dec 20, 2012, 14:17 crypto
 
DangerDog wrote on Dec 20, 2012, 14:05:
I thought I read that you shouldn't defrag SSD drives
It doesn't, it optimizes them... what ever that means.

The software is actually an old version, they are saying that you can upgrade to v16 for 10$ during the promo weekend. So that says to me that you would not get updates and possibly constant upgrade reminders. It might be worth it to customize your file locations but a mistake might end up thrashing your drive to death.
 
Reply Quote Edit Delete Report
 
4. Re: Morning Tech Bits Dec 20, 2012, 14:14 Verno
 
DangerDog wrote on Dec 20, 2012, 14:05:
I thought I read that you shouldn't defrag SSD drives

That's correct, there's no purpose in doing so and it usually conflicts with the drives internal garbage collection. Defragging storage drives in use by third party utilities or raid arrays (Flexraid, Unraid, etc) can still be beneficial in some situations though. For example Flexraid mounts each drive using a virtual driver so Windows no longer controls them directly but depending on the filesystem you're still going to get fragmentation.
 
Avatar 51617
 
Playing: Divinity Original Sin, Destiny, Fire Emblem
Watching: Continuum, Star Trek TNG, Haunt
Reply Quote Edit Delete Report
 
3. Re: Morning Tech Bits Dec 20, 2012, 14:05 DangerDog
 
I thought I read that you shouldn't defrag SSD drives  
Avatar 6174
 
Reply Quote Edit Delete Report
 
2. Re: Morning Tech Bits Dec 20, 2012, 12:43 Verno
 
O&O is good because it can defrag drives as devices so if you've got them mounted in a raid array or proprietary software then it won't mess with integrity.  
Avatar 51617
 
Playing: Divinity Original Sin, Destiny, Fire Emblem
Watching: Continuum, Star Trek TNG, Haunt
Reply Quote Edit Delete Report
 
1. Who still defrag these days? Dec 20, 2012, 12:30 Rhialto
 
I may took a quick look if a HD defrag would help once a year, and if so, I use Defraggler. Even the one included in Windows does the job.
I can't comment about SSD though...

But hey, it's free so thanks to O&O for the offer, I think their goal with this is to sell the updrage to v16 at the same time, which is still a deal.
 
Avatar 23064
 
Reply Quote Edit Delete Report
 
9 Replies. 1 pages. Viewing page 1.
< Newer [ 1 ] Older >


footer

.. .. ..

Blue's News logo