Member Since: Nov 26, 2012
Location: Agusan del Norte, Philippines
Mac Specs: L2012 Mini, i7 2.6Ghz, 8GB RAM, 256GB SSD + 1TB HDD(fusion), dual 23" Samsung LED Displays
02-10-2014, 07:09 PM
Originally Posted by chscag
Yeah Mike, that part of the article surprised me when I read it. That's a good reason for avoiding the small cheap SSDs we often see advertised. It does make me wonder how effective the fusion drives that Apple offers are? It seems to me unless you opt for a large fusion drive, you may be better off spending money on the same machine with better standard specs.
Fusion drive has its pros and cons. But here is the short and simple version. The fusion drive what I can tell works as a JBOD array with one exception. The Flash storage side of the fusion drive works as disk cache. So when files are moved onto the fusion drive they are moved first to the flash storage, then later the data is then moved to permanent storage on the regular HDD part of the array. As far as the OS is located. Don't shoot me if I am wrong, but I don't think all of the OS is on the flash storage side, I know the kernel and pretty much all the kernel modules must be on the flash storage to start the JBOD up. But I believe the rest of the OS like the built in applications are actually located on the HDD side of the house. Which corresponds with many claiming its fast, but not as fast as a pure SSD.
So the pros are that data is fast getting written (at least until the buffer is full). Faster then normal startup. Much larger storage without multiple drive locations.
The cons, slow read speeds common to HDDs. MTBF is double due to two disk in the JBOD array.
Now in regards to why SSDs are faster the larger they are. I think this has to do with independent memory banks working in parallel with each other. Thus creating more memory bandwidth and thus faster transfer speeds. If I am explaining this correctly..
I knew this when I got my Samsung 256GB 830 series, but 512 was the largest then and way to over priced. Plus I think at the time the 512 was only about 50 to 100MB/s faster. Perhaps due to other reasons, so I am not certain. But the 256 was the best price/performance/capacity at the time.
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