Apple machines - "disc" storage

[Dave2002]

Out of devilment I went on to the Apple site, and tried to configure a new iMac for very high performance and storage. It's possible to get the price to over £3k for a Retina display 27 inch model with maxed out memory etc.

What I'd really like to know is about the performance of the storage nowadays. According to Apple, their latest SSD storage is considerably faster than their previous generation systems. However there is a size limit of 1 Tbyte. On the other hand, there is a 3 Tbyte Fusion drive option.

I have some experience of SSD drives over the last few years, but only limited experience of the Fusion drives. For really heavy duty work (complex video editing say) is SSD the only way to go, or would Fusion drives give almost the same performance at less cost, and provide more significantly more storage? Fusion drives may work well enough for every day tasks, but not for some really large ones. I don't know - not yet, anyway.

Maybe nobody here has tried the kind of video processing which would reqiure such computer power.

It may also be the case that software could have a very significant impact, with different software packages performing more or less well. One task which I tried to do recently was to remove the shakes from a 12 minute HD video. The actual processing on my fairly fast machine took about 12 minutes, but the results are not particularly good. I don't even know if it's possible to get good results, but it might just work out if the parameters are shosen well, or at least better. Conceptually it ought to be possible with a careful alignment algorithm over successive frames, but with 1800 frames per minute, the 12 minute video would have 21600 frames to check - each in HD. If it was vital, then brute force manual work at say 15 seconds for each frame alignment would take 450*12 =

For a task like that it might make sense to split the whole video into short sections and then try the processing on small sections to evaluate how well it all works. Then either all the sections could be processed separately then joined together, or if a good set of parameters is found, the whole video could be processed with that set applied.

It may also be the case that some software for reducing camera shake effects is much more effective than others. My own immediate needs are limited, and probably would not justify spending a huge amount of money to get a very high performance machine. I do have some videos I'd like to clean up, if possible, but there are other solutions - including just not bothering on cost and time grounds!

Another "solution" would be to wait a few years, and exploit Moore's "Law" - performance/price ratios could be 10 times better in 5 years time!

[Anastasius]

I had to look up what a Fusion Drive was!

This article I found very helpful http://www.techradar.com/news/comput...ur-mac-1154051

Seems to me that it is effectively a 3GB SSD unless you are editing massive images etc that won't fit in the 128GB SSD.

[Dave2002]

Interesting, but the article is a few years old. I don't know how far the modus operandi for these drives has been uncovered, but my understanding was that they are a form of multi-level (2) storage system - essentially a form of virtual memory system. Very probably sections - blocks - whatever (Apple don't say) are all copied to the hard drive, though since the hard drive is slower than the flash memory that might be done on a schedule, in fhe background. When "live" storage runs low then read only blocks can be deleted from the flash memory as there will already be a copy on the backing disc. If a copy hasn't already been made, then a copy will be made before it is deleted. If the block is R/W, then it might still be possible to find out if there have been any changes since the last read from disc. If not, then the block can be deleted from the flash, otherwise it will be written out to disc before deletion.

In order to gain a speed advantage the most active data and program sections are most probably the ones to be kept in flash memory.

The algorithms Apple use to optimise the running have not been disclosed AFAIK, but they are very probably some form of working set model.

On the technical side of the hardware, it's possible that Apple might upgrade the flash memory, or put more of it in the fusion drives. This is unknown. Having more flash memory would increase the likelihood that progams and data would stay in the flash memory (working set), while having faster flash memory would give a very significant speed increase. I notice that Apple claim that the more recent flash memory they are using in new machines is 2 to 3 times faster than that from three years ago.

Some of the original reviews of fusion drives suggested that some types of program could hit a performance road block, which would effectively reduce the computer speed to that of a disc drive based system, though most would not. I recall that is related somehow to the size of data written out in short time. If, however, the programs which are desired to be run are (say) video processing, and if they have the characteristics which hit that road block, then there would be little point in using the fusion drives for that kind of program. Apple and others haven't been too forthcoming about some of the details, or how well things work under heavy load conditions.

[Dave2002]

I just found this - http://9to5mac.com/2015/10/13/retina...e-you-serious/ - which suggests that new iMac machines with Fusion drives actually have only a relatively small amount of included flash memory compared with previous models - 24 GBytes. This might impose quite a serious hit on performance compared with earlier Fusion drives, though this is uncertain and would depend on the user, applications and data. Maybe that's to entice people who are aware of this to install more SSD memory, rather than a compromise solution.

Would 24 Gbytes be sufficient for demanding tasks? For many people even 24 Gbytes would probably be good enough, as there are now moves towards more main memory - 8Gbytes even up to 32 Gbytes, so for some applications most of the program instructions and data could be loaded into main memory. The claimed faster speed of the SSD/Flash memories in the more recent Fusion drives might also have a benficial effect for some applications. Where possible limitations of a 24 Gbyte included SSD/Flash would become more apparent would be for data approaching or exceeding 24 Gbytes, which is perhaps most likely to be HD video data or batch image data.

Tasks which require high speed streaming of more than 24 Gbytes of data through the processor would effectively be slowed down to the speed(s) at which data could be read and/or written to the hard drive - which is likely to be significantly slower than the solid state memory. Workarounds to mitigate against this potential problem could be to process the data in chunks not exeeding 24 Gbytes, and also to make sure that any non crucial tasks and data were not loaded during the processing of tasks requiring high speed throughput. Perhaps 95% of users would be unaffected more than 90% of the time, with the assumption being that users who really want to have better performance will buy higher specced machines with more SSD, or Mac Pro machines, or even a non Apple alternative.

Another possible "solution" would be for Apple to allow an upgrade within machines to install SSD after initial purchase, though either for technical or commercial reasons this is something which Apple has been restricting for recent models over the last few years.

[MrGongGong]

Another possible "solution" would be for Apple to allow an upgrade within machines to install SSD after initial purchase, though either for technical or commercial reasons this is something which Apple has been restricting for recent models over the last few years.

I have a refurbished macbook pro with a 1TB SSD that was installed after initial purchase
There's nothing to stop you doing that (apart from the warranty).

[Dave2002]

I have a refurbished macbook pro with a 1TB SSD that was installed after initial purpose.
There's nothing to stop you doing that (apart from the warranty).

MrGG

Hi - yes - that's fine for MacBook Pros - and if you look on Amazon you'll find that there's a firm offering SSD upgrade kits for various models of MacBook Pro - see for example - http://www.amazon.co.uk/Transcend-Je...acbook+SSD+kit

I may try that next year as my machine reaches its 3rd birthday.

I think this may be harder for new iMacs, as Apple have used soldered connections and glue - so I hear/read - in some of the newer models. I have upgraded an old iMac successfully with main memory (push fit, though brute force was needed to extract the old memory, and also to push the new back in), and I think the others I have are upgradeable, but some of the ones from around 2011 on are perhaps much more difficult to make changes to. I have assumed so far that if the Crucial site checks my machines out that if there is a suggested upgrade, that it will be possible to carry it out - http://uk.crucial.com/