256 GB Flash vs 1 TB Fusion

[gnasher729]

Not flaming; just curious: has this actually been tested? The reason I ask is because that 4 GB of write cache is on the SSD, no? So how would that make any writing to the FD faster than a pure SSD?

Because of the way SSD drives work.

An SSD drive can read 4KB blocks very quickly, it can write 4KB blocks into an empty block quickly, and it can erase pages of typically 128 KB. If you have a page with 32 blocks and want to overwrite a block, the SSD drive can't do it. It's just physically impossible. An SSD drive can't write to space that already contains data. What it would have to do is read the other 31 blocks, erase the page, write the 31 old blocks and the new one. (Of course, the firmware on an SSD drive will do whatever it can to avoid the situation; old drives had massive slowdowns on writes because of that).

Fusion has 4GB of already erased space ready. So if you write many small blocks, they can be written into that erased space at full speed. Then when the drive is not busy, it can do the hard work without you waiting for it.

 

[badlydrawnboy]

Because of the way SSD drives work.

An SSD drive can read 4KB blocks very quickly, it can write 4KB blocks into an empty block quickly, and it can erase pages of typically 128 KB. If you have a page with 32 blocks and want to overwrite a block, the SSD drive can't do it. It's just physically impossible. An SSD drive can't write to space that already contains data. What it would have to do is read the other 31 blocks, erase the page, write the 31 old blocks and the new one. (Of course, the firmware on an SSD drive will do whatever it can to avoid the situation; old drives had massive slowdowns on writes because of that).

Fusion has 4GB of already erased space ready. So if you write many small blocks, they can be written into that erased space at full speed. Then when the drive is not busy, it can do the hard work without you waiting for it.

Thanks for this. I had no idea a Fusion drive could actually be *faster* than an SSD. Do you know where I can read more about this? I"m curious.

 

[toddzrx]

Because of the way SSD drives work.

An SSD drive can read 4KB blocks very quickly, it can write 4KB blocks into an empty block quickly, and it can erase pages of typically 128 KB. If you have a page with 32 blocks and want to overwrite a block, the SSD drive can't do it. It's just physically impossible. An SSD drive can't write to space that already contains data. What it would have to do is read the other 31 blocks, erase the page, write the 31 old blocks and the new one. (Of course, the firmware on an SSD drive will do whatever it can to avoid the situation; old drives had massive slowdowns on writes because of that).

Fusion has 4GB of already erased space ready. So if you write many small blocks, they can be written into that erased space at full speed. Then when the drive is not busy, it can do the hard work without you waiting for it.

Right; got it. Is any of this related to TRIM support in any way?

Thanks for the info.

 

[RoryO]

I'm also wondering about the noise difference. Some say it's noticeable, others not.

From my experience of a 27" 3TB Fusion 2013 iMac. The difference is totally noticeable. About 80% HDD noise and the remaining 20% fan noise. The 80% is unpleasant to my ear, an ambient electrical hum. The fan noise is a more pleasant quiet whoosh of air.

If you can hear the fan on an iMac you will very much notice the difference with the HDD as well. If you can't hear the fan or don't mind HDD noise in general, then maybe you won't "notice".

At the end of the day the HDD drive sounds like an HDD drive (wiring / humming) and the SSD like an SSD (silent).

If you want to know if you'll notice the sound just grab any hard drive and put it on your desk, spin it up and that's what its likely to sound like. Obviously choose a drive of the same form factor and size to get a good comparison. (I understand 2.5" HDDs are quieter than 3.5" drives).

 

[roland.g]

I have received my 1TB Fusion drive. Machine checks out well. No screen issues etc. As for the noise, there is none that I can tell to report of. Looks like the reports to the contrary were most likely individual incidents, possibly of a bad drive or an issue from a Time Machine restore or Migration Assistant copy. But it seems that my HDD is spun down when not actively being used as I can not hear it at all.

BTW - does anyone know the Terminal command that will allow you to see the volume written to / activity on the HDD portion of the Fusion drive?

Thanks.

 

[badlydrawnboy]

I have received my 1TB Fusion drive. Machine checks out well. No screen issues etc. As for the noise, there is none that I can tell to report of. Looks like the reports to the contrary were most likely individual incidents, possibly of a bad drive or an issue from a Time Machine restore or Migration Assistant copy. But it seems that my HDD is spun down when not actively being used as I can not hear it at all.

BTW - does anyone know the Terminal command that will allow you to see the volume written to / activity on the HDD portion of the Fusion drive?

Thanks.

Glad to hear this as I just ordered an iMac with 3 TB Fusion. I read a lot of reviews that said the Fusion drive was nearly silent, so the previous post claiming it's noisy worried me.

 

[iamgalactic]

Glad to hear this as I just ordered an iMac with 3 TB Fusion. I read a lot of reviews that said the Fusion drive was nearly silent, so the previous post claiming it's noisy worried me.

I really wouldn't worry about it unless you're sitting in a totally silent room listening intently - and who does that?

My 2xLacie 2Big external drives make far more noise than my late 2012 1TB Fusion iMac, as does any music I listen to whilst working.

I think there may be some iMacs out there that make excessive amounts of noise because they're borked - but I don't think it's normal.

 

[PatriotInvasion]

At the end of the day the HDD drive sounds like an HDD drive (wiring / humming) and the SSD like an SSD (silent).

After much debate, I decided to order my 27" iMac with a pure 256GB SSD instead of the 1TB Fusion Drive. While it would be nice to have everything internal, I can't go back to hearing a grumbling HDD in a Mac in 2014 after spending the past year+ with the all SSD 13" rMBP, iPad, and iPhone. I owned a mid-2010 27" iMac and that drive noise bugged the heck out of me.

Plus, 256GB will double the on-board storage that my 128GB rMBP had, and I have a 1TB LaCie Thunderbolt HDD that I can use to store large media files I access once every 3-4 months. In fact, I see that as making good use out of the 2 Thunderbolt I/O ports that factor into the price of the iMac anyway. Also, for anyone worried about the space constraints of 256GB or desk clutter of external HD's, an Apple Time Capsule as your home router can also act as your resource for occasional large files that don't need to sit idle on your Mac. Just be sure you have those backed up!

Lastly, I'm banking on a pure SSD iMac being better for resale value down the line since that's where all Macs are headed. I think even a 256GB SSD will sound better than a 1TB Fusion to a potential buyer 3 years from now. When the iMac goes all SSD, they'll probably start out at 256GB anyway.

 

[PicnicTutorials]

Get to the flash hands down. 256 is a bit on the small side but should suffice 99% of the time. I have everything installed with a fare amount of apps and have only used 100G of my flash. Just get a external and put all other junk on it. The PCI ssd drive is much fasts than the fusion. At least all the youtube vids I watch comparing the two said so.

 

[PatriotInvasion]

Get to the flash hands down. 256 is a bit on the small side but should suffice 99% of the time. I have everything installed with a fare amount of apps and have only used 100G of my flash. Just get a external and put all other junk on it. The PCI ssd drive is much fasts than the fusion. At least all the youtube vids I watch comparing the two said so.

Well, the Fusion is now 128GB of PCIe as well, but just don't want to hear constant grumbling from the HDD as it decides what apps and files to transfer between the two drives. I can easily make 256GB work for 90% of what I do. If I have to pull out my Thunderbolt external HDD or access something on my 1TB Time Capsule every now and then, so be it. I'd rather have a silent Mac with no moving parts in 2014, but the Fusion is a nice stop gap solution and option for those that would prefer not to worry about storage.

 

[Montymitch]

I know I'm late to the party, but my 2012 with Fusion is quiet. It is incredibly quiet. Even when the fans ramp up, its quiet.
I'll let you guys hash out what is faster and why, but my machine rips along nicely without making a sound.

 

[yjchua95]

This result is from my iMac with a 256GB SSD.

Still faster than a Fusion, at any rate

 

[joema2]

...
From what I've read, the read speeds of the Fusion drives are equivalent to PCI-flash (700 MB/s), but the write speeds are about half as fast...

I guess I don't really know where those slower write speeds would show up in my usage, if at all.

Reads outnumber writes by 5:1 or 10:1 on typical systems. You can verify this yourself by running Activity Monitor and comparing read vs write data. I just rebooted my iMac and rendered an HD video in FCP X and exported 213 raw photos in LightRoom. Data read: 11.6GB vs data written: 3.61GB.

If writes are 1000x faster but that only comprises 10% of your I/O, the maximum speed up is less than 10%.

 

[p3ntyne]

This result is from my iMac with a 256GB SSD.

Still faster than a Fusion, at any rate

Wow! You're really proud of that screenshot.

 

[PatriotInvasion]

Reads outnumber writes by 5:1 or 10:1 on typical systems. You can verify this yourself by running Activity Monitor and comparing read vs write data. I just rebooted my iMac and rendered an HD video in FCP X and exported 213 raw photos in LightRoom. Data read: 11.6GB vs data written: 3.61GB.

If writes are 1000x faster but that only comprises 10% of your I/O, the maximum speed up is less than 10%.

Yea, at least for me, the decision to go pure SSD internally was based mostly on principle, not real world speed performance. I just don't want a spinning disk in my Mac anymore...especially one that requires surgery to replace if it has problems like the recall on the 1TB Seagate drive in my mid-2010 27".

Basically, anyone's decision should come down primarily to storage needs and appetite for managing storage with an external drive should 256GB become tight. Any write speed boost that pure SSD provides should just be considered a bonus, not a reason to buy.

For me 256GB is more than enough space to enjoy 90% of the time. For the 10% of the time I need to access large media files, I'll open my desk drawer and pull out my LaCie Thunderbolt drive and plug it in. If I don't feel like doing that, the media files will be a few clicks away on my Time Capsule.

 

[ioannis2005gr]

The Fusion drives are just a stop gap solution until ssd prices become more cost effective...within 5 years all computers will use ssd!

....within 2 years the max! I chose 256GB PCIe SSD + external storage (via USB/Thunderbolt).

 

[p3ntyne]

....within 2 years the max! I chose 256GB PCIe SSD + external storage (via USB/Thunderbolt).

IMO, there will always be people using one faster drive and one bigger, slower one - weather its one pci-e ssd and one sata ssd etc.

I'm not sure if Apple will do this, but I'm sure some people will.

 

[DDaddyx2]

I've been really happy with my 1 tv fusion drive. Seems pretty fast to me. 256gb SSD would mean you'd save your data to an external.

 

[PatriotInvasion]

Picked up my BTO 27-inch baby tonight with the 256GB SSD. Compared to the mid-2010 model I sold a year or so ago, this thing is gorgeous and dead silent. The mid-2010's Seagate 1TB HDD (eventually recalled) sounded like a clogged lawnmower.

Not to mention this thing is blazing fast at everything. Very happy.

 

[ventuss]

256MB is fine if you don't plan on bootcamp gaming.