Reply to post: Re: And still putting...

Re: And still putting...

It's only the cache that is an SSD style on the hybrid drive. You WILL notice the difference from a 5400RPM drive to a full on SSD

The point I was replying to was one which said there would be no advantage in a hybrid drive (i.e. one with a small amount of flash storage working as a persistent cache for a conventional spinning disc) having the spinning part working at anything faster than 5,400rpm. We all know that just about any SSD will thrash just about any HDD in most real-world tests, whether the HDD is 5,400, 7,200 or 10,000rpm.

It's obviously a fairly complex interaction and I have no experience of Apple's drives, only the Momentus XT, which I have installed a couple of times. In this disc there is a - by modern standards - very small amount of flash (i.e. 4GB or 8GB) which is only used during reads. Writes go straight to the spinning disc for security / consistency reasons.

In concept I suppose it's a bit like ReadyBoost, but done in the drive's firmware rather than by the OS.

4GB is probably not enough to cache all the parts of OSX, Photoshop and whatever else might be loaded on startup, so some items will come straight from the spinning disc each time.

In those cases (always write-through, some reads coming from rust) moving from 5,400rpm to 7,200rpm absolutely will make a difference, though I believe that Seagate's later offerings were "intellispin", rather than fixed speed.

Another poster pointed out that Apple's drives come with 32GB or 128GB SSD. With that amount of "cache" it's entirely possible both that OSX and key applications will fit in their entirety into the SSD, and that writes can go to the SSD by default, with the drive "archiving" to rust during idle moments. In this case there will be very little performance benefit from 7,200rpm over 5,400rpm, and the slower speed should result in lower power consumption and possibly longer life; the SSD is likely to outlast the rust anyway.

Interesting. I'll have to investigate. The beauty of the Momentus XT was that it was entirely transparent to the operating system, appearing simply as a normal SATA drive. I even have one fitted to my RiscPC. Other "hybrid" drives have needed OS drivers. I wonder which type this is?

M.