I don't know of any software that does that automatically but I do know of several people doing that sort of thing, especially if they have multi-boot systems like developers. It's probably best done using the command line and doing manual links (read the man page on the "ln" command), in fact I don't even know if it's possible to do it with the user interface. I suppose you could transfer stuff off one drive to another and create aliases, but I've never tried it.
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Drive Failed, considering hybrid - what to look out for?
- Thread starter BradHatter
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I have a multi-boot system. Right now Mountain Lion is on my internal SSD and every other OS partition since Snow Leopard is on an external. I was thinking of yanking the optical and putting in a fast HDD as well.
Having all my data split across different OS volumes is a pain. Eventually some will be removed.
Having all my data split across different OS volumes is a pain. Eventually some will be removed.
mafaky
macrumors regular
How does it work?
I currently have approx. 45GB data on Apple's Mail app Folder plus another 18GB data on Thunderbird app Folder in my rMBP. These are increasing day by day; as I have to save and store most of my incoming and almost all of the outgoing mail. Plus I have another 15-16GB in the Documents folder, also slowly increasing... I have a further 50GB of music in my PC. This also will be increasing gradually.
So, let's assume I buy a new Mac Mini with the 1TB FD. Can I transfer all the contents of Apple Mail. Thunderbird, Documents as well as iTunes contents to this 1TB drive (actually: ..."to the flash storage part of the 1TB drive") and keep on using these apps without any constraints? (AFAIK, the FD has only a 120-128B flash storage...) Or some of these folders need to stay in the mechanical HDD part of the drive?
Or should I consider to use my current and upgrade my late-2102 Mac Mini which can be upgraded to a 2-drive configuration: use a 256GB or 512GB SSD for Mac OS X and for storing all the above mentioned "heavy data storages" in the SSD and spare its 1TB HDD (of my current Mac Mini) for other usage?
Thank you.
😕
I currently have approx. 45GB data on Apple's Mail app Folder plus another 18GB data on Thunderbird app Folder in my rMBP. These are increasing day by day; as I have to save and store most of my incoming and almost all of the outgoing mail. Plus I have another 15-16GB in the Documents folder, also slowly increasing... I have a further 50GB of music in my PC. This also will be increasing gradually.
So, let's assume I buy a new Mac Mini with the 1TB FD. Can I transfer all the contents of Apple Mail. Thunderbird, Documents as well as iTunes contents to this 1TB drive (actually: ..."to the flash storage part of the 1TB drive") and keep on using these apps without any constraints? (AFAIK, the FD has only a 120-128B flash storage...) Or some of these folders need to stay in the mechanical HDD part of the drive?
Or should I consider to use my current and upgrade my late-2102 Mac Mini which can be upgraded to a 2-drive configuration: use a 256GB or 512GB SSD for Mac OS X and for storing all the above mentioned "heavy data storages" in the SSD and spare its 1TB HDD (of my current Mac Mini) for other usage?
Thank you.
😕
A Fusion Drive is a virtual drive that combines an SSD and an HDD into a single volume. The volume spans the two drives. The Fusion Drive will manage which files are on the SSD at a given instant and which are on the HDD, without your knowledge. Items that are accessed frequently are moved to the SSD and those that aren't are moved to the HDD. This is all done automatically.
The good part is they're generally quick, the bad part is that at a given instance you don't know which file is on which device. If a problem develops with either the SSD or the HDD then it will need a full restore from backup.
The good part is they're generally quick, the bad part is that at a given instance you don't know which file is on which device. If a problem develops with either the SSD or the HDD then it will need a full restore from backup.
When fooling around with various OS releases I noticed that a Fusion Drive causes the kernel to use significantly more memory on Mountain Lion and Mavericks. About 500MB is my estimate. I haven't tried it on Yosemite.
grahamperrin
macrumors 601
Actually, I'm quite sure it's by design. I took the Fusion apart because I'm constantly playing with stuff so I'll try to remember to look at that the next time I put together another.
Here's something interesting (quite interesting, IMH0) that I found:
Putting an SSD into an external USB 2.0 housing and connecting it to a USB 2.0 system, formatting it, and then booting it like that (non-Fusion) with Mavericks or Mountain Lion would typically take nearly a minute for everything to boot to the login screen. This is slower than if the drive was connected internally. The speed delay I assume is because the USB port is bottlenecking the SSD. If the same housing is using a fast Hitachi 2.5" drive (one of the new ones that uses AF format) the boot speeds are comparable. This is why I think I can confirm the bottleneck on the SSD is the USB port.
Now, if I combine the external USB 2.0 based SSD with an external (and slow) HDD to make a Fusion drive with it, the system would boot in just over 40 seconds, which is considerable faster. I rebooted like this several times to confirm it.
I have to assume that Core Storage/Fusion is implementing some type buffering or maybe using a much larger "virtual" sector on the Fusion drive that makes it behave faster. Obviously, that's a guess, but the speed increase is noticeable during boot. The point being Fusion seems to do more than just map data between an SSD and a hard disk drive. I have seen similar sorts of performance gains on striped RAID sets but I haven't compared them one-to-one.
Were backup drives consistently connected during this test? Backup drives, especially with multiple boot options delay booting because the kernel has to interrogate all of the possible boot options before it proceeds booting. You have to compare apples with apples.
I'm not saying you're wrong, it just seems at least superficially a little weird.
I'm not saying you're wrong, it just seems at least superficially a little weird.
All was done with the external drive disconnected so that wasn't a factor. The Fusion is just faster.
It's too bad there's no easy way to see what drive is being hit when using Core Storage. I would speculate that Core Storage may offload some code, like kernel type stuff directly into RAM and my be running it from there, not the drives. Why do I say this? I noticed that with later versions of OS X if you're accessing a file continually from an external drive, if the OS is new enough, the drive smart enough (SAT compatible), and the file small enough, eventually the OS will offload the file from the drive and put it into its own RAM. I observed this at least on Mavericks and I assume it's on Yosemite and maybe ML too. By watching the drive lights initially a particular file was slow like you'd expect. Then it got somewhat faster, and I assume this is because it's been moved to the external HD's cache. Then it got very fast and the drive lights stopped blinking, indicating that the drive wasn't being accessed at all yet the file was still being read. By cacheing a file like that in RAM they'd not only get an obvious speed advantage but they would also be cutting energy as no more drive access was needed.
If this was done with Core Storage Fusion as well, but maybe cacheing more stuff, like system caches, it could explain the speed gain and the memory use.
A shot in the dark for sure, but that might explain it.
Last night I formatted the same SSD with Snow Leopard to see the boot speed when inside the USB 2.0 enclosure and the boot speeds were comparable to a similar HDD, so the USB is the cause of the bottleneck. The theory about Fusion unloading some stuff and putting it in RAM makes sense. All experiments I've done with Fusions have been on Mountain Lion and later, and they all boot slower than Snow Leopard.
grahamperrin
macrumors 601
Recommended reading
Seek unified buffer cache and/or UBC in Mac OS X Internals: A Systems Approach (Amit Singh)
Brendan's blog » Top 10 DTrace scripts for Mac OS X (2011-10-10, highlights)
BSD Overview: Kernel Programming Guide: Differences between OS X and BSD; "... The Unified Buffer Cache implementation in OS X differs from that found in FreeBSD. "
Hacking the Mac OSX Unified Buffer Cache - Tenerife Skunkworks (2008-03-04, highlights)
BlackChair - Defeating the Mac OS X Unified Buffer Cache (almost) (2008-10-11)
Also, from 2000 (but note, above, the differences between OS X and BSD):
Yet another excellent and informative post, Graham. Now I know what I was observing wasn't just my imagination. Thanks.
Any write ups like those on Core Storage and Fusion technology? About all I seem to be able to find is stuff like "the fusion drives maps items frequently accessed to the SSD and leaves other items on the HDD" and that's about it.
Last night I put El Capitan on the Fusion I mentioned earlier. It booted in slightly less than a minute, but then again it's a beta release.
WD is working on a PCIe based hybrid SSD:
http://www.storagereview.com/wd_to_demonstrate_4tb_hybrid_hard_drive
4TB HD coupled with 128GB SSD.
The more I think about hybrids the more I'm beginning to like the idea.
http://www.storagereview.com/wd_to_demonstrate_4tb_hybrid_hard_drive
4TB HD coupled with 128GB SSD.
The more I think about hybrids the more I'm beginning to like the idea.
Although I think that's a performance comment, it does fit into the "what to look out for" category because I'm not certain a standard SATA drive would connect to one of those PCI ports without some type of adapter, if it would even work at all.
This seems to be a decent article on SATA express and SATA for anyone interested:
http://www.extremetech.com/computin...dard-promises-dramatically-faster-performance
http://www.extremetech.com/computin...dard-promises-dramatically-faster-performance
I think he moved to PC BSD. I noticed a post by him on one of their web sites.
If you care about keeping the optical drive and want the performance benefit of an SSD and HDD fusion drive look for a WD Black 2. They are discontinued but interesting. It is a 120gb SSD and 1TB 7200 RPM HDD in a single 2.5" chassis. It wasn't supported in OS X at first but there is a firmware and driver for it now. Some places have it for $139 and it can be configured as a fusion drive.
Some of these drive manufacturers seem for some reason to be failing to advertise the capabilities of some of their products. I never even heard of that thing but it sounds hot, if you know what I mean. I can't afford to go 100% SSD because of the cost/space factor but something like that is an option, and yet I never heard of it.
This thread is actually several months old and the issue was resolved with a 500GB Hitachi because they're pretty fast for a regular HDD and, more importantly to the owner, dirt cheap. I think it was just over $50.
Out of curiosity, do you have a part number for that drive? There's a post on the iMac section where someone was thinking about putting something like that in and he has a link from WD to the drive. It didn't say anything about being discontinued so maybe it's a newer model.
Just curious.