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A few notes on SSDs in Laptops
I've now had the SSD in my laptop for about 10 days. Its made a massive difference to the way I work.
Its striking as to how much of a difference having this extra performance in the laptop would make. In march I upgraded the memory on this laptop from 2GB to 8GB - which also made a massive difference, specially since I almost never reboot the device and the filesystem cache get very good at handling just the right kind of stuff - but what kills them is my email ( ~ 30 gb ) and VMs ( upto 5 running at any given time ). Having the SSD now means that I no longer need to drop back to 10 seconds for jedit startup after I've been running a couple of VMs.
One thing that hasn't gone quite to expectation is the battery life. The HP 2540p had ~ 4 hrs or so, doing what I do, when I got it new. That had dropped to just over 3 hrs with the 250gb sata disk in. With the SSD its now gone to 2 hrs ~30 min or so. Initially that felt quite strange, I was expecting it to go in the other direction. And while I havent been able to put a finger on exactly what this is, it seems like there are 2 interesting side effects from the SSD upgrade.
1) The four cores on this i5 laptop now run at full speed ( 2.53 Ghz ) a lot more often than they did in the past, trending this over the last 48 hrs and its averaged 1.87Ghz; Not sure what it was earlier but the cpu governors used to stay blue a lot more than they do now.
2) Heat. The cooling fan is on a lot more, and the heat vent seems a lot warmer than it ever did in the past. This might be due to the cpus running a lot faster, a lot more. The disk itself does not 'seem' to be any warmer. The bottom left side of the laptop which houses the disk feels cool.
The big win of-course, is performance of everything. Almost every app just starts in place ( even eclipse! ). Doing a search in large code projects is instantaneous. Git operations are visibly quicker. Even using svn isn't nearly as boring as it used to be, if I can stop adding -a to all my svn commits it would not get in my way.
The only thing that isn't quite as quick as it needs to be on this machine now is the graphics interface ( intel HD ).
Also worth keeping in mind is that use CentOS-6 for the SSD hosted content, and make sure you have 'discard' enabled as a mount option.
- KB
29/Aug/2011 08:07:45 am, 10 comments
The 4 cores running more often is possibly because they are spending much *less* time waiting for the I/O to be ready (iowait)? Not a performance guru (as you know :-) but just my guess.Interesting that you are running jEdit? What were the reasons behind that? Was vim not good enough?
yes, the 4 cores running at higher clock rate is exactly down to most things now being cpu bound rather than i/o ( and in some cases on Network.I use Vim as well, I use Eclipse as well. But mostly I like Jedit, it works. Only thing missing really is a good git plugin
Could the CPU thing be due to TRIM ? Ah, I was thinking I'd get an email if you replied to this thread, but I wasn't sure so I checked manually (I would have forgotten all about it otherwise). I guess you have that turned off. 
Surprisingly (to me and you at least) most SSD eat a lot of power, even in idle mode.The manufacturers just ignored power consumption and are still starting to wake up from this mistake :(
Manu,I have ext4/discard on - afaik, that should take care of the trim stuff.
Sam,
Do you have some stats / details to share about the power issue ?
We got the same issues; overheating and slower access on Laptops with Solid State Drives running Centos.Scientific Linux and Fedora definitively load and run slower than it should be, on laptops with SSD, but I did not check the temperature of the SSDs.
Running Debian Squeeze on SSD laptops shows significant higher speed and absolutely no heat from SSD..
I thought it may be the kernel versions, but Fedora has newer kernel than Debian, but it is still slower, however I did not check the temperature of the SSD running fedora.
It seem that all RedHat derivatives shows a slowing down of speed and heated SSDs.
Since we were not aware about this issue, this is just a empiric report, but we can do more rigorous quantification and analysis, to draw the right conclusions.
Meanwhile, if anyone has solutions or explanations, it would be great, I would like to know them.
Have you tried using the laptop with the noop I/O scheduler since you have a SSD? Depending on your usage, your overall I/O should improve even further.Unfortunately, this means more batter drain for you :P
Interesting about the power thing, I guess the increased cpu cycles probably explain this. 
That thing with the CPU - yes, that is a thing that has to do with I/O. I have desktop that I decided to upgrade in order to use for video rendering. Before I upgraded, I had a dual core Pentium CPU @2Ghz. When I was rendering both cores were maxed out. When I upgraded to a Quad Core Q9650, I was expecting much faster rendering times - obliviously. But guess what - rendering times did not change very much - I got a 10% performance increase at most. Turned out that all 4 cores were running at about 35-40% at most, while the HD was struggling to keep up with the data flow. Now I need an SSD too :)