Dell Mini 9 Discussion Discussion on the Dell Inspiron Mini 9.
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Join Date: Feb 2009
Re: thank goodness no more defragment.... - 03-01-2009, 11:37 PM
Oops I guess the wording of my question made me sound kind of clueless. Yea I know what an SSD and an HDD are and the process of defragmentation. I just didn't fully understand why an SSD didn't need to be defragged but now it's clear.
Join Date: Nov 2008
Location: New Hampshire
Re: thank goodness no more defragment.... - 03-02-2009, 12:05 AM
Another consideration is that SSDs have a large, but finite, number of write cycles and unnecessary writes to disk are to be avoided.
Mini 9|2GB RAM|64GB RunCore|Intel 5300|Windows 10
Join Date: Feb 2009
Re: thank goodness no more defragment.... - 03-02-2009, 03:42 AM
First it might be helpful to define what defragmentation is, and why it happens ....
When a traditional filesystem looks to allocate a file, say ext3, ntfs, or hfs, generally the block allocation routines will look for sequential blocks (filesystem block size here - 4k or 8k depending, not disk sector size 512B.) The filesystems look for sequential blocks because while a disk can provide > 100MB/s in sequential data (the heads line up, and read a cylinder or more of the disk in progression) they can provide only 100-150 I/Os a second if seeks are involved. Said another way, at 4k reads, 100MB/s is ~25,000 I/Os a second versus 150. That's more than two orders of magnitude.
I point this out because SSD are just different!
With SSDs (and we can talk about erase cycles some other day), the performance of an I/O for a random seek are ~1ms, instead of ~8 ms like on a physical spinning media, meaning, in my previous comparison, that the 'cost' between a non-sequential I/O and a sequential I/O is much, much closer.
If the costs of a these I/O types are about on par, there's little need to physically reorganize the layout of the media to increase the sequentially (ala defrag.) This becomes even more appealing when you realize flash drives have limited write cycles.
Join Date: Mar 2009
Re: thank goodness no more defragment.... - 03-03-2009, 06:23 PM
There are two types of 'fragmentations' when you use an SSD:
a) file system fragmentation that affects NTFS/FAT, which is what most of us know and hate :lol: , and
b) internal [physical] fragmentation of the data in the SSD that is a result of wear levelling.
Both are independent of each other. In a SSD, wear levelling will occur regardless of the OS.
And file system fragmentation in Windows will occur regardless of the storage subsystem, be it SSD or HDD.
There is nothing we can do (or that needs to be done) about the wear levelling, since it's designed to conserve the life of the SSD.
File fragmentation has little effect on SSD read times and for sequential writes because of the very low latency of the SSDs. Random write performance for SSDs, is unfortunately not that good. Free space fragmentation of the filesystem causes writing of the data in smaller parts (random writes) rather than as a whole large file (sequential) due to the increased I/O requests issued by the filesystem, and this can decrease SSD write performance over time. This is because of the mismatch in the cluster size of the filesystem (usually 4kB for NTFS) and that of the physical blocks of the SSD (larger than 4kB), resulting in a time-sapping erase-write operation to accomodate even a small 4kB file.
See the discussion here:
http://www.diskeeperblog.com/archives/2 ... is_al.html
So, while file fragmentation is not necessary for SSDs, free space consolidation at the file system level is said to help.
Join Date: Mar 2009
Don't stop defragging just yet... - 03-05-2009, 09:06 AM
Wonderfully put Dislocation.
To anyone reading, don't give up the defragmentation regimine altogether!
I recommend to clients/friends to just change their schedule...
Instead of once a month, I have them do it every 3-4 months...
Besides, there's a HUGE misunderstanding of the Life Cycle of SSDs.
Some stats refer to "Write (Erase) Cycles" others refer to "Write Cycles" and many people think that they are the SAME.
They are not the same. Anyone here who understands how NANDs work understands the difference. Combine that with "Wear Leveling" and the difference between SLCs and MLCs and the recipe gets even muddier.
Besides, as I understand it, "Statistically Speaking", less than 10% of the "AVERAGE DAILY USE" of a PC is made up of writes. (Yes, PC. Be it a NetBook/Laptop/Desktop/Mac/etc... Servers are not included)
I'd like to "GUESS" that most NetBook owners are using their NetBooks for *LESS* than 2-3 hours daily. That's about 18 minutes of writes. Forgive me for not doing the math, but in a "Real World" scenario, worrying about the SSD from your NetBook crapping out on you is a waste of time. What's the average "Laptop" replacement schedule, 3 years?
I'd like to think that even if you defragmented weekly your SSD would make it 3 years! :lol:
PS: Yes, I know some of you will use your NetBook/Laptop/Desktop until you kill it, so if you're in THAT particular boat, then you know what you need to do. For the average owner, it just isn't a concern.
You know it's true....
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