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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > SSDs - State of the Union for Nov 2010.

SSDs - State of the Union for Nov 2010.
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Snow-i
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Nov 5, 2010, 11:42 AM
 
I'm not sure this is the best forum for this - mods feel free to move to another ifn' you care to. Since SSDs can be BTO for macbooks these days, i thought it would be appropriate here.

I have an Aluminum Macbook with a 250gb HDD, and I've been savoring over an SSD for some time now. With Christmas approaching and my lady asking me what I want, it seems the time is nearing for me to swap out my HDD, turn it to an external for backup, and pop in an SSD. I just wish my Macbook had Firewire :-(.

What are the tradeoffs, aside from capacity, with modern SSDs?
What brands seem to perform better than others as far as reliability and performance, if any?
How much will an SSD affect battery performance?
It seems SSDs, much like harddrives, benefit from higher capacities. Is this just a perception or a reality?
If i were to pull the trigger on one, what is the sweetspot (best bang for the buck) in today's market (brand/performance/capacity)?
Should I wait for OS X to offer TRIM support (rumored in 10.6.5)?

I'm probably looking for a 128 or 256 gb. Right now I'm using roughly 60 gb and I can't forsee that increasing very much for the useful life of this machine - I have a Powermac G5 that among other uses acts as a storage machine for anything I don't need on my macbook.
     
CharlesS
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Nov 5, 2010, 12:53 PM
 
The main tradeoff on the Mac right now comes from OS X's current lack of TRIM support. Unlike HDDs, SSDs require an extra step to erase a block once it's been written to, which means that once you've gone through every block on the drive and written to it, write performance starts to degrade as every write needs to be preceded by an erase. TRIM is the solution to that, because it clears out unused blocks in the background after you delete stuff from the drive, reverting them to virgin status. Unfortunately, OS X doesn't have TRIM yet, although it might get it in the future.

What people are often recommending for Macs these days are SSDs using the Sandforce controller. These drives tend to use more of the drive's capacity as spare blocks, which sacrifices capacity but gives you more spares to work with once you've used up all the blocks making up the drive's capacity. SandForce also uses a compression scheme to minimize the amount of data written to the drive, so that it takes a lot longer to use up all the blocks and invoke the write penalty than on most other SSDs.

There's also the 256 GB Crucial RealSSD C300, which is, AFAIK, pretty much the fastest SSD out there. The trouble with it is that write performance gets really hammered once all the free blocks get used up. If you have TRIM support, it doesn't matter, but on OS X you're taking a gamble that Apple will implement TRIM before you start to invoke the penalty. The other thing about the C300 is that it's the only SSD to support 6.0 Gbps SATA, which means if you ever transplant it into a newer machine that has 6.0 support (with an OS that supports TRIM), it will really scream. Unfortunately, current Macs only support 3.0 Gbps SATA, so you don't see all the raw performance with this drive.

For your needs, I'd probably go with SandForce. There are a large number of drives that use this controller, but OCZ's generally seem to be well spoken of.

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mduell
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Nov 5, 2010, 02:17 PM
 
Originally Posted by Snow-i View Post
How much will an SSD affect battery performance?
Slight improvement.

Originally Posted by Snow-i View Post
If i were to pull the trigger on one, what is the sweetspot (best bang for the buck) in today's market (brand/performance/capacity)?
OCZ Vertex 2 240GB OCZSSD2-2VTXE240G for $450.
     
CharlesS
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Nov 5, 2010, 02:20 PM
 
^ Wow, that's a good price.

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P
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Nov 6, 2010, 11:58 AM
 
SSDs have been dropping recently, probably in anticipation of the new 28nm Intel drives and the SandForce 2000 controller, both of which are just starting to appear.

Seconded on the OCZ/Sandforce recommendations. With a larger drive with good garbage collection (such as the SandForce), TRIM support is not so crucial. As long as you keep some 10% free (the more the better), you won't feel the lack of TRIM.

It seems SSDs, much like harddrives, benefit from higher capacities. Is this just a perception or a reality?
Reality, but that speed increase is only transfer bandwidth.The big gain for SSDs is access latency, which is not affected by drive size.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
Snow-i  (op)
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Nov 8, 2010, 01:02 PM
 
Originally Posted by mduell View Post
That looks to be a screamer of a drive, but 450 is a little steep for me at the moment. I can also get by with 128 - i don't use that much space and I'm going to turn my current 250gb into an external.

Why does there seem to be such a huge disparity between read/write times when browsing through SSDs? Is this because of newer MLC technologies pushing the envelope on speed? That said, what is a realistic sweet spot for my Macbook's SATA 3.0gb/s connection vs newer, faster SSD drives. Will I have to worry about saturating that connection?

What are my approximate sequential read/write times for my current HDD? Its a 5400rpm 250gb HDD (stock for 2.4ghz alu macbook 5,1 (2008)). I know SSDs really outperform on random reads and write thanks to not having to physical parts to move, but I'm trying to get a handle on the stats for these drives and the realized performance gains.
     
Snow-i  (op)
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Nov 8, 2010, 01:07 PM
 
Originally Posted by P View Post
SSDs have been dropping recently, probably in anticipation of the new 28nm Intel drives and the SandForce 2000 controller, both of which are just starting to appear.

Seconded on the OCZ/Sandforce recommendations. With a larger drive with good garbage collection (such as the SandForce), TRIM support is not so crucial. As long as you keep some 10% free (the more the better), you won't feel the lack of TRIM.



Reality, but that speed increase is only transfer bandwidth.The big gain for SSDs is access latency, which is not affected by drive size.
Which is why SSDs so overtly outperform HDDs on random reads and writes, right? If I do pull the trigger (or have it gifted) then I'll likely go for a 128 or there abouts model and keep my space usage to a minimum. I sure hope 10.6.5 has TRIM - even if I never have to use it, itll be good for SSDs on OS X.
     
mduell
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Nov 8, 2010, 01:15 PM
 
OCZ Vertex 2 120GB OCZSSD2-2VTXE120G for $235

Originally Posted by Snow-i View Post
Why does there seem to be such a huge disparity between read/write times when browsing through SSDs? Is this because of newer MLC technologies pushing the envelope on speed? That said, what is a realistic sweet spot for my Macbook's SATA 3.0gb/s connection vs newer, faster SSD drives. Will I have to worry about saturating that connection?
I don't understand what you mean by "read/write times." Do you mean sequential read/write speeds? Or access time?
3Gb/s SATA is a bottleneck for most current SSDs, but that's not really the concern. The time you really notice the SSD isn't when you're getting 250MBps instead of 60MBps (ok, you might if you do that a lot), it's when you're getting 20MBps instead of 0.3MBps.

Originally Posted by Snow-i View Post
What are my approximate sequential read/write times for my current HDD? Its a 5400rpm 250gb HDD (stock for 2.4ghz alu macbook 5,1 (2008)). I know SSDs really outperform on random reads and write thanks to not having to physical parts to move, but I'm trying to get a handle on the stats for these drives and the realized performance gains.
Probably ~50MBps when it was empty, ~30MBps now that it's partially full.
     
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Nov 8, 2010, 01:49 PM
 
Originally Posted by Snow-i View Post
Why does there seem to be such a huge disparity between read/write times when browsing through SSDs?
What is your question - why reading is faster than writing? Because for Flash, you have to delete before writing - so 2 operations instead of 1. In addition, while you can read or write single bytes, you have to delete an entire block at once. SSDs have all sorts of trick to hide this issue - that's where the expensive controllers come in - but it can affect write performance, especially if the drive is almost full.

Originally Posted by Snow-i View Post
Which is why SSDs so overtly outperform HDDs on random reads and writes, right?
Correct. Random reads and writes are a measure of the access time. As a rule of thumb, harddrive access times are in the milliseconds, flash access times are in the microseconds and RAM access times are in the nanoseconds.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
CharlesS
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Nov 8, 2010, 09:57 PM
 
Originally Posted by P View Post
Seconded on the OCZ/Sandforce recommendations. With a larger drive with good garbage collection (such as the SandForce), TRIM support is not so crucial. As long as you keep some 10% free (the more the better), you won't feel the lack of TRIM.
This I am skeptical of. Unless the drive's firmware knows about HFS+, how can its garbage collector know what blocks are unused and thus able to be cleared?

My understanding has been that the advantage that SandForce provides is that it reduces the amount of actual writing that is done via compression.

Originally Posted by Snow-i View Post
Why does there seem to be such a huge disparity between read/write times when browsing through SSDs? Is this because of newer MLC technologies pushing the envelope on speed? That said, what is a realistic sweet spot for my Macbook's SATA 3.0gb/s connection vs newer, faster SSD drives. Will I have to worry about saturating that connection?
Some drives use older SSD controllers which are not as well performing, which causes them to have much slower speeds. You want to make sure to get either a SandForce or Marvell controller at this point (and SandForce is probably the right bet for what you described as your needs). Additionally, most current SSDs only have SATA 3.0 Gbps on them — I think the only one that supports 6 Gbps right now is the Marvell controller used by Crucial — so your MacBook's SATA card will not be a bottleneck.

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Snow-i  (op)
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Nov 8, 2010, 11:06 PM
 
Originally Posted by mduell View Post
OCZ Vertex 2 120GB OCZSSD2-2VTXE120G for $235



I don't understand what you mean by "read/write times." Do you mean sequential read/write speeds? Or access time?
3Gb/s SATA is a bottleneck for most current SSDs, but that's not really the concern. The time you really notice the SSD isn't when you're getting 250MBps instead of 60MBps (ok, you might if you do that a lot), it's when you're getting 20MBps instead of 0.3MBps.
Originally Posted by P View Post
What is your question - why reading is faster than writing? Because for Flash, you have to delete before writing - so 2 operations instead of 1. In addition, while you can read or write single bytes, you have to delete an entire block at once. SSDs have all sorts of trick to hide this issue - that's where the expensive controllers come in - but it can affect write performance, especially if the drive is almost full.
.
Sorry for not being more clear - I was speaking of different models of SSDs as I'm browsing newegg. Some advertised speeds are far less for around the same price points. Question was answered though.
     
Snow-i  (op)
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Nov 8, 2010, 11:08 PM
 
Originally Posted by CharlesS View Post
This I am skeptical of. Unless the drive's firmware knows about HFS+, how can its garbage collector know what blocks are unused and thus able to be cleared?
This was my train of thought too. I thought the OS managed allocation and such?

My understanding has been that the advantage that SandForce provides is that it reduces the amount of actual writing that is done via compression.
This I heard too, but wouldn't this just be delaying the inevitable without TRIM support?

Some drives use older SSD controllers which are not as well performing, which causes them to have much slower speeds. You want to make sure to get either a SandForce or Marvell controller at this point (and SandForce is probably the right bet for what you described as your needs). Additionally, most current SSDs only have SATA 3.0 Gbps on them — I think the only one that supports 6 Gbps right now is the Marvell controller used by Crucial — so your MacBook's SATA card will not be a bottleneck.
This is what I was thinking, but Newegg is usually right on top with updating prices.
     
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Nov 9, 2010, 05:35 AM
 
Originally Posted by CharlesS View Post
This I am skeptical of. Unless the drive's firmware knows about HFS+, how can its garbage collector know what blocks are unused and thus able to be cleared?

My understanding has been that the advantage that SandForce provides is that it reduces the amount of actual writing that is done via compression.
SandForce controllers do lots of clever things, and I don't think anyone really knows what contributes to their excellent performance. As I understood idle garbage collection, the drive queries the operating system about whether a specific LBA is currently in use or not. This is the only way that makes sense to me - the drive cannot be expected to guess all filesystems, partition maps and configuration settings - but whether the ATA specification allows for something like that is more than I know.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
Big Mac
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Nov 9, 2010, 05:39 AM
 
What's taking Apple so long to deliver what appears to be a very important SSD feature?

"The natural progress of things is for liberty to yield and government to gain ground." TJ
     
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Nov 9, 2010, 06:18 AM
 
Originally Posted by Big Mac View Post
What's taking Apple so long to deliver what appears to be a very important SSD feature?
TRIM means that the filesystem driver sends an extra SATA command for each block deleted. If adding that support takes time, perhaps the filesystem people are busy doing something else? HFS3 (aka Mac OS Extreme) in Lion.

To be fair, Apple has only really embraced SSDs in the last few months. 10.6.5 is rumored to add TRIM, and it's so late that 10.6.6 is already in beta. Programming is like this - sometimes you find bugs that are hard to fix.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
CharlesS
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Nov 9, 2010, 01:01 PM
 
Originally Posted by Snow-i View Post
This I heard too, but wouldn't this just be delaying the inevitable without TRIM support?
Well, Apple implementing TRIM is also inevitable. You just want to delay one inevitability enough that it takes longer than the other one.

The other thing is that even after you start invoking the write penalty, you're still not getting as much of it with SandForce because you're not doing as many writes.
Originally Posted by P View Post
SandForce controllers do lots of clever things, and I don't think anyone really knows what contributes to their excellent performance. As I understood idle garbage collection, the drive queries the operating system about whether a specific LBA is currently in use or not. This is the only way that makes sense to me - the drive cannot be expected to guess all filesystems, partition maps and configuration settings - but whether the ATA specification allows for something like that is more than I know.
I dunno about that — seems to me that if you need to code support for something into the OS anyway, you might as well just implement TRIM. My understanding has been that the garbage collection knows about the NTFS file system and uses that to determine what blocks can be cleared, and thus doesn't do anything on the Mac. I could be wrong, of course, because my understanding of this is admittedly not very extensive.

edit: Here's an article I found, although it's admittedly old: link

That's for Indilinx, of course. I wasn't able to find anything equivalent for the SandForce drives, but this article seems to imply that SandForce's also requires NTFS.
( Last edited by CharlesS; Nov 9, 2010 at 01:18 PM. )

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Nov 9, 2010, 01:55 PM
 
My understanding was that idle GC exploited an existing ATA function to query the OS, but that this was less efficient than being told which sectors to clear.

In any case, this OCZ Summit firmware update explicitly enables idle garbage collection on Mac OS X. Either they implemented support for HFS+ on that specific firmware, or it is something special in the ATA specification. Other OCZ drives note Mac compatibility and display logos.

That the text does not mention any Linux systems is curious, but I don't know how to read it. Either they support by filesystem, and efs2/3/4 is not supported, or they simply don't support Linux at all.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
CharlesS
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Nov 9, 2010, 09:54 PM
 
The OCZ Summit, according to Google, uses a Samsung controller. Apple's been known to use Samsung SSDs in some of their machines, so it wouldn't surprise me if Samsung built in some support for HFS+ in their SSDs.

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CharlesS
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Nov 10, 2010, 08:19 PM
 
Originally Posted by P View Post
10.6.5 is rumored to add TRIM, and it's so late that 10.6.6 is already in beta. Programming is like this - sometimes you find bugs that are hard to fix.
Sadly, 10.6.5 still doesn't seem to support TRIM (at least not on my machine). I hope we don't have to wait until Lion for this.

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Snow-i  (op)
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Nov 11, 2010, 03:29 AM
 
It would be a shame if we did. Something tells me it might be its own update - if not, 10.6.6 is already in beta (so i hear).
     
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Nov 11, 2010, 04:18 AM
 
Originally Posted by CharlesS View Post
Sadly, 10.6.5 still doesn't seem to support TRIM (at least not on my machine). I hope we don't have to wait until Lion for this.
That is disappointing. Apple tends to support things like this when their own hardware will benefit, and the recent SSD focus made me think it was about time.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
Maflynn
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Nov 11, 2010, 08:06 AM
 
Originally Posted by P View Post
That is disappointing. Apple tends to support things like this when their own hardware will benefit, and the recent SSD focus made me think it was about time.
Agreed and so that's why I'll be down right surprised to see TRIM support built into 10.7
~Mike
     
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Nov 14, 2010, 09:24 PM
 
is it possible to do a "manual" TRIM? The OS or filesystem knows about what needs to be trimmed, so it should be possible to run a shell script to do it from time to time?
     
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Nov 15, 2010, 07:04 AM
 
Some manufacturers have applications for XP that do a manual TRIM, but I'm not aware of one for OS X.
The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
     
Snow-i  (op)
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Nov 15, 2010, 03:17 PM
 
Hmm, that could be a potential market for an indie developer - if Apples drags their feet until Lion. How hard would it be to make a TRIM utility? Perhaps it would be a great item to put on the upcoming Mac App Store. Any developers here?
     
CharlesS
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Nov 15, 2010, 04:05 PM
 
Any such tool would need to be extensively, exhaustively tested, since the slightest mistake would lead to data loss. This would make it very difficult indeed.

It would also be nearly impossible to get such a tool to pass the App Store rejection guidelines.

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Big Mac
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Nov 15, 2010, 08:39 PM
 
Yeah, such a proposed utility would never get on to an App Store. Ever.

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