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Does low ram matter with SSD?

J

JesseW6889

macrumors 6502
Original poster
Dec 12, 2010
317
0
When you run out of ram, it starts to use the hard drive, right?

But isn't SSD the same thing as ram? If I got the 2gb MBA AND I used more than 2GB would it really make a difference?
 
The SSDs that Apple use provide about 200MB/s bandwidth. Single-channel DDR3 provides 8.55GB/s (8550MB/s). RAM is over 40 times faster! Another thing is latency. 1066MHz DDR3 with CAS latency of 7 (assuming that it's that Apple uses, at least they do with other Macs) has latency of ~6.6ns while Intel SSDs (couldn't find info about the ones that Apple use) have latency of ~75µs. That's 75 000ns! Again, RAM has over million times better latency.

Okay, that's it for theoretical stuff. Having an SSD definitely helps since it's much quicker than HD but RAM is still much faster. If you already know that you will be using more than 2GB, then pay the extra hundred bucks and get 4GB. Furthermore, only 1.75GB of that 2GB is usable because 320M takes 256MB.
 
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ram is still important however I have a 2gb and maxed it out by opening multiple programs and it still operated smoothly. I wouldnt worry about 4gb unless you plan on doing alot of heavy work (which really isn't suited to the air anyway) or if you plan on doing parallels
 
Also remember that more RAM reduces the number of page outs to the SSD. SSDs lose performance over time as they are written to over and over again. It may just be a few gigabytes here and there, but it can add up.
 
Fair enough... but as far as I am concerned my SSD seems to work instantaneously anyways (even at 7500000 whatevers!)

So, i mean, REALLY would I notice a difference if I ran out of ram and the system had to use the SSD?
 
dukebound85 said:
does ram suffer from the same "fatigue" as ssd's do?
Click to expand...

Short answer: No.

Long answer: Nooooooooooo.

Google it.

edit:


iTouch.Myself said:
Fair enough... but as far as I am concerned my SSD seems to work instantaneously anyways (even at 7500000 whatevers!)

So, i mean, REALLY would I notice a difference if I ran out of ram and the system had to use the SSD?
Click to expand...

Yes, you would notice as the SSD will slow down massively under OSX without TRIM support. It clogs up fairly fast.
 
dukebound85 said:
does ram suffer from the same "fatigue" as ssd's do?
Click to expand...

Short answer is NO, RAM does not suffer from write fatigue. The longer answer is that write fatigue in SSD's is of little importance in real world usage.

cheers
JohnG
 
So... to reiterate:

Yes I understand that IF I regularly use more than 2gb of ram I should get 4gb...

BUT,

If I sometimes went over the 2gb, would It make a NOTICEABLE (read:upsetting) difference if the system had to use the SSD pagefile?

I get that ram is volatile and a billion times faster, BUT, I dont notice any wait time accessing files from the SSD, would I notice any wait time if the OS was using the SSD instead of ram (once it had used up the 2 gb)
 
iTouch.Myself said:
So... to reiterate:

Yes I understand that IF I regularly use more than 2gb of ram I should get 4gb...

BUT,

If I sometimes went over the 2gb, would It make a NOTICEABLE (read:upsetting) difference if the system had to use the SSD pagefile?

I get that ram is volatile and a billion times faster, BUT, I dont notice any wait time accessing files from the SSD, would I notice any wait time if the OS was using the SSD instead of ram (once it had used up the 2 gb)
Click to expand...


Here's how I look at it. I used a Rev B MacBook Air with the older SSD for 2 years as my sole home computer. It was fine for everything but running Windows in virtualization. XP and later 7 worked fine in Boot Camp on that older Air.

However, what sold me on the Rev D was the 4GB option. 2GB is fine for now, but I'm likely to skip the Rev E MacBook Air and wait for the Ivy Bridge version (I'm guessing the Sandy Bridge version will be a mostly incremental upgrade). 4GB makes virtual machines run faster, and it also gives me some "future proofing," which I find important since the CPU is already yesterday's technology (so why hobble it even further?). For $100, yes, it pads Apple's margins by about $75, but it might let me defer another $1700 purchase by a year.
 
Xeperu said:
Short answer: No.
Yes, you would notice as the SSD will slow down massively under OSX without TRIM support. It clogs up fairly fast.
Click to expand...

What is this I don't even...

I have been doing a bit of research on SSDs recently and I can say that this is an absurd statement. The lack of TRIM support will NOT hinder performance noticably; from what I've seen, there is no evidence to support that a TRIM service increases day-to-day performance.

On the issue of SSD wear: Most modern SSDs have a usage life of ~41 years. Seagate, WD, Corsair, etc... are all capped at about that point. That means that you would have to completely dump content onto the SSD, fill it to maximum capacity, then wipe the drive and do it again... all day... every day... for 41 years.

SSD wear is alarmingly exaggerated.
 
Will MBA ever be user-upgradeable?

Is there a reason for the inability to upgrade RAM post-purchase, other than the "Mac tax?" I know for my iMac I can get much cheaper RAM from other suppliers. I think I am going to go for the 4 GB just in case, which sucks since I am not sure how heavy duty my usage is going to be.
 
mjillard said:
Is there a reason for the inability to upgrade RAM post-purchase, other than the "Mac tax?" I know for my iMac I can get much cheaper RAM from other suppliers. I think I am going to go for the 4 GB just in case, which sucks since I am not sure how heavy duty my usage is going to be.
Click to expand...

Mostly it's the whole, "no ram slot, soldered to the logic board" thing.
 
Thanks KPOM, your answer comes the closest to at least addressing the topic at hand.

As far as SSD's are concerned, I am not speaking of actual durability... nor am I about volatility, or upgradability!

What I want to know is... when my MBA runs out of useable ram, and HAS to use the SSD, does anyone KNOW if the speed degradation is significantly noticeable?

I'll go a step further and define 'significantly noticeable' as the appearance of a beach ball, or any other type of waiting / loading.

I am using a new 13" with 4gb of ram and occasionally go over the 2gb mark... I am interested in getting an 11" with only 2gb of ram, and dealing with the SSD handling the page file when the system needs more than 2GBs of ram, BUT that isn't an option if it will mean a change in the otherwise very smooth, hitch free operation that I have come to expect from my current air
 
johnnymg said:
Agreed.............................

I've seen a small decrease (<10%) in the xbench drive score of the Crucial C300 SSD in my MBP in over 9 months of use.

cheers
JohnG
Click to expand...

I'd call 10% pretty massive in these days of computing.
 
Xeperu said:
I'd call 10% pretty massive in these days of computing.
Click to expand...

Not when you take into account the fact that a 10% slower SSD HD is still massively faster than even the fastest regular platter based HD's. So no it's not that bad as you like to describe here.
 
iTouch.Myself said:
What I want to know is... when my MBA runs out of useable ram, and HAS to use the SSD, does anyone KNOW if the speed degradation is significantly noticeable?

I'll go a step further and define 'significantly noticeable' as the appearance of a beach ball, or any other type of waiting / loading.

I am using a new 13" with 4gb of ram and occasionally go over the 2gb mark... I am interested in getting an 11" with only 2gb of ram, and dealing with the SSD handling the page file when the system needs more than 2GBs of ram, BUT that isn't an option if it will mean a change in the otherwise very smooth, hitch free operation that I have come to expect from my current air
Click to expand...

Every machine will be slowed down if it doesn't have enough RAM and has to access the hard drive instead. With an SSD drive the effect is less than for disk-based drives, because you will have lots of accesses to small amounts of data, and that is where the advantage of SSD to disk-based drive is the greatest. I'd guess there may be situations where you can _notice_ a delay if you look for it, but whether you would find such a delay annoying would be up to you.

Now a bit of good news: If you start Activitiy Monitor, and check your memory usage, there is a certain amount used for what is called "Wired Memory". That amount will be less when you have less RAM, so where your 4 GB machine uses 2.2 GB, a machine with only 2 GB would just about fit that into its 2 GB RAM.
 
gnasher729 said:
Now a bit of good news: If you start Activitiy Monitor, and check your memory usage, there is a certain amount used for what is called "Wired Memory". That amount will be less when you have less RAM, so where your 4 GB machine uses 2.2 GB, a machine with only 2 GB would just about fit that into its 2 GB RAM.
Click to expand...

Good note.

Also: A lot of people just look at the "Free" RAM in Activity Monitor. Correct me if I'm wrong, but both the "Free" and "Inactive" count as memory that's not being used and is utilizable.

Right now, mine says "Free: 363MB, Inactive: 270MB", so I have ~630MB RAM to use freely. Which is a lot.
 
johnnymg said:
Agreed.............................

I've seen a small decrease (<10%) in the xbench drive score of the Crucial C300 SSD in my MBP in over 9 months of use.

cheers
JohnG
Click to expand...

You do realize your C300 has one of the best if not the best SSD controllers? That the Toshiba controller Apple puts in the Air is pretty much 2nd tier with regards to write amplification and performance. Another factor is how "full" was your C300? SSD's tolerate wear much more evenly if not fully filled up to capacity. That's much easier with a 256gb C300 vs. a 64gb Apple/Toshiba Air drive. For the OP, unless you're going to be a "tax cheat" and buy the air out-of-state to save on sales tax, just man up and get the 4gb for the "measly $100" if you're planning on using the air for a decent amount of time. Many of the posters here are on Apple's "hamster annual hardware update policy" If you're in that camp, then get the 2gb and sell the air in a year as the best resale % is on the lower spec machines.
 
magbarn said:
You do realize your C300 has one of the best if not the best SSD controllers? That the Toshiba controller Apple puts in the Air is pretty much 2nd tier with regards to write amplification and performance. Another factor is how "full" was your C300? SSD's tolerate wear much more evenly if not fully filled up to capacity. That's much easier with a 256gb C300 vs. a 64gb Apple/Toshiba Air drive. For the OP, unless you're going to be a "tax cheat" and buy the air out-of-state to save on sales tax, just man up and get the 4gb for the "measly $100" if you're planning on using the air for a decent amount of time. Many of the posters here are on Apple's "hamster annual hardware update policy" If you're in that camp, then get the 2gb and sell the air in a year as the best resale % is on the lower spec machines.
Click to expand...

The toshiba controller is actually a very recent one which, in the mba, has been tuned and will actually outperform the latest sandforce controller. Anand has a great piece on this. While I see it as normal not to completely fill up your SSD hardrive. Same as you don't race your car with a cold engine, yes you can do it, but your hardware will break that much sooner.

I completely agree with you on the memory. For me this notebook will have to last at least three or four years. With this in mind I can't see why you wouldn't upgrade to 4GB of RAM. There is no way you can figure out what's going to happen with Apple software demands in the coming three to four years. Yes currently you might be able to work fine with 2 GB but what about in three years time. Remember, you can't upgrade...
 
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