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Can SSDs Be Used For Software Development?
hackingbear writes "I'm considering buying a current-generation SSD to replace my external hard disk drive for use in my day-to-day software development, especially to boost the IDE's performance. Size is not a great concern: 120GB is enough for me. Price is not much of a concern either, as my boss will pay. I do have concerns on the limitations of write cycles as well as write speeds. As I understand, the current SSDs overcome it by heuristically placing the writes randomly. That would be good enough for regular users, but in software development, one may have to update 10-30% of the source files from Subversion and recompile the whole project, several times a day. I wonder how SSDs will do in this usage pattern. What's your experience developing on SSDs?"
I use SSDs for my (both) development systems--the first was for the work system, and after seeing the improvements I decided I would never use spinning-platter technology again.
The biggest performance gains are in my IDE (IntelliJ). My "normal" sized projects tend to link to hundreds of megs of JAR files, and the IDE is constantly performing inspections to validate the code is correct. No matter how fast the processor, you quickly become IO-bound as the computer struggles to parse through tens of thousands of classes. After upgrading to SSD, I no longer find the IDE struggling to keep up.
I ended up going with SSD after reading this suggestion for increasing IDE performance. The general jist: the only way to improve the speed of your programming environment is to get rid of your file access latency.
The real key here is this: when an SSD drive can no longer execute a write - the disk you will let you know. Reads do not cause appreciable wear so you will end up with a read only disk when the drive has reached the end of it's life. This is vastly superior to the drive just dying becuase it's had enough of this cruel world.
I'd be interested to see some statistics on electrical failure of these drives though... but it seems that isn't as much of an issue.
Just got one in a Dell laptop, came with Ubuntu. A subjective overview:
I have no idea how well it performs with swap. I'm not even really sure why I have swap -- I don't have quite enough to suspend properly, but I also never seem to run out of my 4 gigs of RAM.
It's true, the write speed is slower. However, I also frequently transfer files over gigabit, and the bottleneck is not my SSD, it's this cheap Netgear switch, or possibly SSH -- I get about 30 megabytes per second either way.
So, is there gigabit between you and the SVN server? If so, you might run into speed issues. Maybe. Probably not.
Also worth mentioning: Pick a good filesystem if a lot of small files equals a lot of writes for you. A good example of this would be ReiserFS' tail packing -- make whatever "killer FS" jokes you like, it really isn't a bad filesystem. But any decent filesystem should at least be trying to pack writes together, and I only expect the situation to improve as filesystems are tuned with SSDs in mind.
It also boots noticeably faster than my last machine. This one is 2.5 ghz with 4 gigs of RAM; last one was 2.4 ghz with 2 gigs, so not much of a difference there. It becomes more obvious with actual use, like launching Firefox -- it's honestly hard to tell whether or not I've launched it before (and thus, it's already cached in my massive RAM) -- it's just as fast from a cold boot. The same is true of most things -- for another test, I just launched OpenOffice.org for the first time this boot, and it took about three seconds.
It's possible I've been out of the loop, and OO.o really has improved that much since I last used it, but that does look impressive to me.
Probably the biggest advantage is durability -- no moving parts to be jostled -- and silence. To see that in action, just pick out a passively-cooled netbook -- the thing makes absolutely no discernible noise once it's on, other than out of the speakers.
All around, I don't see much of a disadvantage. However, it may not be as much of an advantage as you expect. Quite a lot of things will now be CPU-bound, and there are even the annoying bits which seem to be wallclock-bound.
Don't thank God, thank a doctor!
Before we start, let me make a prediction: You never asked about the MTBF of your hard disk, right...?
http://www.intel.com/design/flash/NAND/mainstream/
a) When Intel says "new level of ... reliability", maybe it means they thought about this problem when they designed the drive.
b) When they say "NAND flash", maybe it means they're not using the cheapest MLC memory as mentioned in that scary wikipedia article.
c) When their datasheet says "Minimum useful life of five years, assuming 20Gb/day of writing", maybe they got those numbers from real engineers, with degrees.
d) When their datasheet also says, "Should the host system attempt to exceed 20 GB writes per day by a large margin for an extended period, the drive will enable the endurance management feature to adjust write performance, this feature enables the device to have, at a minimum, a five year useful life", maybe they were really really paranoid about saying 'five years' because they know people will start class-action lawsuits if it doesn't work out.
So, um, how this even got greenlighted in 2009 is beyond me. It's like 1999 called wanting its flash-myths thread back.
No sig today...
So interested people want to know --- how do you get the "insider" information from an X25-M (ie., total amount of writes written, and number of cycles for each block of NAND)?
I've added this capability to ext4, and on my brand-spanking new X25-M (paid for out of my own pocket because Intel was to cheap to give one to the ext4 developer :-), I have:
/sys/fs/ext4/dm-0/lifetime_write_kbytes
<tytso@closure> {/usr/projects/e2fsprogs/e2fsprogs} [maint]
568% cat
51960208
Or just about 50GB written to the disk (I also have a /boot partition which has about half a GB of writes to it).
But it would be nice to be able to get the real information straight from the horse's mouth.