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Wednesday, September 29, 2010

SSDs life span

Source Edited by G.Abhinav:
For those who don't know, here are the links on how SSDs work, why they've got only limited number of write / erase cycles, and why MLC SSDs have a very short life-span as compared to SLC SSDs.
The entire article is in itself quite informative, and you should read it if you've the time to do so.
So now you know that every write / erase means the clock of doom is ticking closer to zero hour for your SSD. The clock ticks ten times faster if you've got a MLC SSD which is what is relatively common. So to protect the data and money you've invested in your SSDs, you definitely need to make them last longer.
But you've got lots of things in Windows, that are an indispensable part of the OS, that keep writing or erasing data a huge number of times without your knowledge. Most of these can be avoided or at least made to operate in such a way that they don't harm your SSDs, and now we'll look at them:
1. Defragmentation software :
Defragmentation software consolidates files by moving all the fragments of a file to one place i.e., to adjacent sectors in a HDD, or adjacent cells in a SSD. In this process, it erases data from some cells and writes them into other cells. Keep doing it daily or even weekly, you're going to end up exceeding the write / erase cycles too quickly for your liking.
And for SSDs, defragmenting is totally unnecessary. You see, in HDDs, the seek head has to move over various sectors and hence it has a read time in the order of miliseconds. So it'd help reduce this seek time noticeably by defragmentation when you place all parts of the file sequentially in order to eliminate the necessity of searching through the entire platter.
But with SSDs, there are no moving parts and the SSD already knows in which cell each part of the file is written and so seek time is thousands of times still less; it's in microseconds, and so however heavily a file is fragmented, the SSD knows exactly where every fragment is, and any amount of fragmentation is not going to affect the seek time of SSDs and hence read time for that file.
So remember to disable defragmentation of any SSD volume that you might be having.

2. Logs and disk clean up utilities :
Logs are another problem because data is being constantly written to the SSD's cells. If you're going to use some disk clean up utility, it'll simply delete the data in those cells. So those cells would have been made to undergo one write / erase cycle everytime the utility cleans up your SSD. And contnuation of the log will be written to other cells (because of wear-levelling) and they will also be made to undergo similar such unnecessary write / erase cycles.
So the best thing is to do is not maintain logs, but if you do need them, like temperature logs for CPU, GPU, etc.. then see if you can change the directory of where a log file is being written. If you can change it, then ensure that the directory does not point to a SSD volume. But most of the logs are maintained by Windows and can't be relocated and so the best thing to do will be to let them be as such and use the clean up utility a lot less frequently.
3. Internet Explorer browser cache and default downloads folder :
The content of every website visited is written to a small browser cache. Within that cache itself, data gets written and rewritten many times. Add to that the number of times you delete that internet cache (or some disk clean utility does it for you) and you end up with a very large number of write / erase cycles.
So you can change the directory of the browser cache and ensure that this directory does not point to a SSD volume. So now, the temporary internet files no longer get written into your SSD. You should also change the default directory where the files you download are saved to, when using download managers, and let the new directory not be on a SSD volume.

4. Instant messaging :
Whenever you send Instant mesages or have PC to PC voice chats, the typed messages, or spoken sound files are written as very small files to the SSD before being sent to the other person (it's in a folder which is either the installation folder of the IM software or located in Application Data or Local settings) and then they are deleted after the chat.

Again, these write / erase wears SSD cells. Try installing the program in a mechanical HDD instead of SSD if the IM files are saved to the installation folder. If it's otherwise and the files are written inside Application data or Local settings, only the program creator should alter the program to suit SSDs. Additionally, if you've read through the entire article I've linked this post to, you'll find writing of very small packets of data into most MLC SSDs by itself causes problems.
5. Page file :
Page file or virtual memory is a portion of the HDD, or a particular number of cells of a SSD that's used as if it were RAM. Now data gets written, erased and rewritten into the page file a staggering number of times every minute. And this data is the page file constantly changes with the dynamism of the data in the RAM. So your SSD will hardly last a year if it has got the page file in it.
And wear levelling algorithms will constantly change the cells that act as page file and so you'll end up with all of the cells of the SSD worn out completely in the blink of an eye. So the best option is to add 2 GB more of RAM and then disable your page file altogether. This simple step will dramatically prolong the life of your SSDs, even if you have the operating system in it.
Or if you're very particular about having a page file, you can change the drive where the paging file is, and have it on a mechanical drive instead, but beware; applications will suffer lags because the mechanical drive involved is not as fast as the SSD and hence the benefits of a SSD will not be fully realized as it is made dependent on a mechanical drive.

6. Registry :
Now coming to the second biggest, but the most incurable problem of all: the Windows registry. It grows constantly everytime you install programs or even simply use Windows, and data entries are also constantly being deleted from the registry. The rate at which registry entries are written / erased is in itself enough to wear out SSDs within a few years. Add to that the fact these are written in very small packets, and that disk caching will not be of much use here.
This is most bugging because there is nothing you can do to translocate the registry to another directory. So this can be resolved only if Microsoft decides to create upcoming versions of Windows optimized for SSDs with registry whose location is left to our choice at the time of installation of the OS. Until then there's nothing we users can do. Perhaps the statement "if SSDs suck, blame Windows and not SSDs" has a lot more veracity in it after all.
7. Intelligent disk management :
The simplest way of all; just don't move files from one partition to another or install or uninstall, or create or delete files and folders unless absolutely necessary.
SSDs are simply great with marvellous read and write speeds, lightning quick access times, great durability and with enormous endurance wherein they can last almost infinitely when you just keep reading files from it.
But when it comes to writing files and erasing them many times over as in normal usage, the real Achilles' heel of the SSDs are exposed and that's where the trouble begins with them. This happens to be the sole aspect in which HDDs beat them.

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