How do I match read speed of Fusion drive with external storage?

Excellent question.
Waiting to see what good answers come in.
I'm in the same dilemma.

 

It really depends on how much you're willing to spend.

If you want an extremely fast drive that most internal SSDs including the PCI-E based ones in the iMac then go with the LaCie Little Big Disk

You could also go with the LaCie D2 with the SSD add on and get sort of an external Fusion drive. For 3 TB + SSD you're looking at $600 and for 6 TB + SSD you're looking at $800. It is Thunderbolt 2 and both of them over 1000 MB/s which is extremely fast for a good amount of storage.

The problem with both of those are you'd need a NAS or something similar to back it up to as they don't offer any kind of protection from drives failing.

 

LaCie D2 + SSD is not the same as Fusion. It will mount as two separate volumes. You have to divide whether a given file should be on the fast SSD volume or the slower HDD volume.

Fusion is basically the same thing - a small SSD + a large HDD. However, it displays as a single volume and Apple Pixie Dust decides where a given file should be for you . It will move frequently used files to the SSD portion so that the things you are most likely to request can be delivered at SSD like speed. The bulk of your data will still be on an HDD, and when those less frequently accessed files are requested, it is just a plain old single spindle HDD delivering them.

Going with an internal SSD + external storage instead of Fusion just means that you are choosing to manage your storage manually to some degree instead of letting the Fusion drive present your Fast and slow storage as a single volume that it tries to optimize for you.

What sort of files would you be putting on the external storage system if you decide not to go with the fusion drive? It is entirely possible that the data you would store there doesn't really need to be super fast - for instance, you can store HD Video on a single spindle HDD on USB2 and it will playback just fine.

 

I'm not sure that you need the speed; it is a matter of cost as well.

The reason the internal flash memory storage on an iMac or Mac Pro is so fast is that it is PCIe storage; that's an interface used for all sorts of stuff that requires a really really fast pipeline to the brains of the computer. All kinds of stuff use it. Here, it's flash memory. It's different than just a SSD slapped into a drive bay; those are SATA III interfaces, which are slower.

And all those internal SSD drives you see use SATA III. So if you put one in a Thunderbolt 2 enclosure, they still are limited by the SATA III speeds since that's how fast the drive can pump out data.

A RAID configuration can best this, because it's reading more than one disk at once to take advantage of that Thunderbolt 2 pipeline. The fastest I guess would be RAID 0 striping, so you'd have four drives of 1TB minimum for 1TB total storage, and at least one cold spare. And you'd need a backup of that, of course, since it's the least redundant.

But I'd consider whether you'd get much benefit from it if all you're doing is messing with a RAW file, even a very big one. If your software is behaving well and using RAM and/or scratch disk on the fast internal flash memory, it shouldn't have to be reading a lot from your external. Ask around, but it may be that the benefits (at least in speed; there are other benefits related to fault tolerance, etc) of a RAID vs just an external SSD are minimal for this type of work. Take at look at this analysis of RAID 0 SSDs vs single SSDs, and in particular at the application-oriented tests. Although the RAID was faster, and would be if you just copied those RAWs back and forth, picture imports were equally fast between the RAID and single disk.

http://www.tomshardware.com/reviews/ssd-raid-benchmark,3485-8.html

 

The read speed on a Fusion drive is only fast IF the data being read is actually on the SSD portion of the Fusion drive when accessed. If is comes from the hard disk portion, the read speed will be that of the hard disk (much slower). If the file is accessed a couple of times, the Fusion algorithm will attempt to put some/all of the file data blocks on the SSD for future accesses.

To duplicate this on an external drive, you would need to have an external SSD, which wouldn't be quite as fast as the internal PCI drive, but it would still be fast. For even faster speed, you could set up a RAID-0 SSD in an external Thunderbolt enclosure (i.e. Akitia Thunder Duo or LaCie LittleBigDisk) using a pair of standard SSD drives. If you need great capacity which is unaffordable with pure SSDs externally, you could create an external DIY Fusion drive in an external multi-drive JBOD enclosure using a small SSD and a hard disk of your choice. I would probably not use a 128GB SSD as Apple does, but go with a fast 256GB SSD so more data/files would be resident on the SSD portion when accessed.

For max speed ... get the latest LaCie Little Big Disk with the RAID-0 blade SSDs

 

That is what I have on my 2012 768GB SSD iMac ... I have a pair of 840Pro SSDs in RAID-0 with my Aperture Library on them, a 3 TB hard disk for archive stuff and movie files, and a 6TB drive for first-level Time Machine backups all in a Thunderbay IV. It works great and mimics the setup in my other system of a tower Mac Pro (I keep the synchronized).

For backup, I use a Synology NAS and a MacMini with Thunderbay IV RAID-5 as a TM NAS and Time Machine alternates between all 3 destinations.

 

In this article over at http://www.barefeats.com/hard191.html, Rob-ART provides some info where he configured the d2+SSD upgrade as a Fusion drive. Pretty incredible performance.

Granted, LaCie offers this as one external chassis with 2 separate volumes inside - SSD + HDD. Rob's incantations turn it into a Fusion drive with the caveat that this is not supported by Apple or LaCie. This is however equivalent to what others have done for "roll-your-own" Fusion configurations.

I've done something similar with a refurb Little Big Disk v1, where I replaced one of the 2 HDD with a Samsung EVO SATA SSD. Inside are a 2TB HDD and a 256GB SSD. Of course performance is great for the first 256GB of storage.

 

Well with that 5K monitor you'll want photos and videos to match, which means new cameras with bigger formats, which means bigger RAW files, which means you'll double your storage needs really fast

Just a question of whether you can fill your storage as fast as your credit card balance

The benefit of external is you could start slower, and see with some skillful management if you really need the pricier options. Rarely used files sitting on SSDs don't make much sense.

 

That would certainly work if you can fit all your stuff onto 500GB, plus allowing for some overhead.

But you can have one library or catalog (dunno what software you're using) and the photos on many different disks if you're using any DAM that supports referenced images (I think all do). So you get the benefit of speedy previews, searches, etc etc with the more spacious HDDs for photos you aren't currently using. Especially if you catalog is on the internal PCIe based flash, since it's probably the fastest.

 

The cost of 1TB internal SSD plus external 960GB SSD plus OWC enclosure is very roughly equal to the cost of a 256GB SSD iMac plus a Thunderbolt 2 8TB Pegasus R4. In RAID 5 the formatted capacity is about 6TB. The FD is a little faster on *cached* reads, but much slower on writes. The R4 is more consistently fast over a wide range of tasks.

 

Sorry, I don't know. That does sound like a very fast configuration.

However -- I have a 5D3 and shoot lots of video and raw stills. I would not over-emphasize the I/O aspect, because many common tasks are CPU bound. E.g, in Lightroom if you import CR2 files and build 1:1 previews, it is more CPU-bound than I/O bound.

You can examine the CPU vs I/O state of these activities using the utility iStat Menus.

You want fast I/O but only to the extent it's not the weakest link. Once over a certain threshold, further I/O performance increases don't make much difference -- you are waiting on CPU, GPU, etc.

Whether you are running RAID5 or SSD or whatever, it also should be backed up.

 

OP,

This thread has been very helpful to me since I'm trying to sort through my options as I get ready to buy a new 5K iMac and a Thunderbolt 4 RAID system. I do a ton of photo and video work.

Anyway, I did want to point out one thing. I know your super-smart and already know this, but perhaps this may help others that read this thread.

Thunderbay IV is the OWC's Gen 1 array that uses the Thunderbolt 1 standard.
Thunderbay 4 is the OWC Gen 2 array that uses the Thunderbolt 2 standard.

It's easy to confuse both of them when typing, and I've seen that throughout this thread, but there is a very important difference between the two in terms of speed. Just wanted to point that out so an unknowledgeable user doesn't accidentally purchase the Thunderbay IV if they want the TB2 standard!

Bryan