well,... I think there are many opinions here, but I prefer to have them on my internal drives.
I have 2 internal HDD in my HP laptop, which is very convenient. (I always have an external drive with me as backup to plug in a CDJ)

As I usually play with 2x CDJ 2000 and the SL1 connected, attaching another device caused some crashes because the USB power was too low.

I remember one day, I used to have also an external and brought my laptop to the club, but forgot my HDD home which was still connected to my desktop PC because I was copying some files.....

An advantage would be if you have an internal SSD with your OS and 1 external HDD and 1 as backup, which would be very stable.
Also the advantage of an external drive is that you are able to connect it to your desktop PC, to copy files quickly, or if your OS crashes you can plug it just into a CDJ (if FAT32 formatted)....

I think it´s everybody´s own choise and you need to think what´s the most convenient for you.

I hope though that the next generation SX will have a USB port. This is convenient if DJ´s switch, laptops crash or other reasons.

IMO, Internal only, sized properly to handle all your media, externals just add another layer of possible issues with added controllers and cables. I only use externals to act as a completely isolated storage source in case any internal drives fail.

I replicate my song libraries across 7 drives to for redundancy.

Great info guys! I'll transfer everything to my laptop's internal and keep the external with me as a backup.

Glad I could help.
Just a little tip, make 2 seperate partitions
1 for your OS and 1 for your music.
I install once per year a fresh windows (saved as an image after a fresh installation)
Which is done within 1 hour and I don´t need to copy the music files.
Also setup the download folder to your music partition. ;)

Cheers!!

Sorry, have to disagree with you guys on this - External all the way baby ;) Reason? The OS & Serato DJ are using the HDD & I think the CPU finds it easier to read from another source. It's the same theory as is in practice with most Ultrabooks & Apples Hybrid HDD system - 1 drive to handle processing,etc (SSD) & another for bulk storage (HDD), except your internal HDD will be doing the grunting whilst your external HDD hosts :)

+10
On both systems, MAC and Windows, I highly recommend an external HD, if you have the resources to install a SSD for your OS please Do It, your system will be more efficient and your lap top will have less chances to freeze.
I used for a while the internal HD on my Mac Book pro and I noticed a few glitches. After I switched to external HD those glitches went away.
I will not go in to details, every user has different results depending on its configuration and filing system.
Good luck to you.

External uses Serial BUS resources.. Every time a hardware interrupt is thrown for it, guess where the bus attention goes? Not to your controller..

I agree, but remember, it all depends on the configuration.

I can't logically comprehend a 'but' in a standardized hardware platform. Interrupts are thrown to signal a devices desire for attention where the CPU will then hand over the bus to the device until it's request is fulfilled. This is done on a firmware level and the more devices you pile onto that bus shooting out interrupts there WILL be traffic on the bus. It's bad enough most drives are SATA now which adds another device to this bus that was not there prior. Now you're suggesting 2 serial drives on the bus along with your controller. People can't understand why audio information streaming to and from the controller sound card is interrupted. Madness..

I respect your opinion and I see your point, but on my experience my configuration is working for me and is working better than using an internal HD. Thats why I use decent amount of buffer (256), precisely because I understand what you are talking about.

firewire external no probs at all

100% true

YOU are assuming everyone is running an SSD. All 7 of my laptops are still rotating platters. My external 2.0 drives benchmarks show 30MB/s (USB 2.0 bandwidth limitation) vs my internal at 124MB/s (SATA 3). Internal drives have higher IRQ command task (windows anyway). This isn't like memory where you get a dual/triple channel based on config. Internal trumps USB. USB 3.0 port and USB 3.0 external drive (which most don't have) brings the argument closer, but still falls down based on IRQ settings.

Show me benchmarks to convince me otherwise. The whole SSD and bulk drive are due to SSD size limitations, not performance gain. When SSD's hit 1TB or greater (at a reasonable cost), the whole dual drive argument goes right out the window.

Wrong......wrong......wrong.....you clearly don't know anything about IRQ structure. If the internal IRQ for a HD and a USB device are thrown (lets just agree) at the same exact time, the HIGHER priority IRQ devices gets handled first......guess which one that is?.....The internal HD, because it has a higher IRQ (denoted by a lower value where 0 is the greatest, 1 is the next greatest so on and so forth) than USB.

While this article is dated, it still shows the basic theory:

en.wikipedia.org

Clearly I don't. Thanks for the dated article that only handles firmware level IRQ assignment and doesn't touch base on software level control of the bridge in the least. You should contact Microsoft and tell them that my SATA drive belongs on TOP of the USB host controller in my IRQ tree.

Device manager says it all, software tasking can be used in any time division application, but any hardware flag that hits trumps any software task. I'll leave the Microsoft suggestion in your hands if your that interested in that change, I've tasked my systems properly and don't need that suggested change.

I'm not assuming anything other than they are using some type of external storage - flash, HDD, SSD.. - I only mentioned the SSD as part of my example outlining the reasoning of behind opinion.

Even guys using CDJ's swear external HDD o/ USB Flash Drives / even SD/ XCSD cards load music quicker than through internal HDD.

Um.....does a CDJ run windows or Mac...? Last time I looked they were standalone units.....apples and submarines.

What, you've never heard of using CDJ's with software? What would you suggest they play timecode CD's on? apples, submarines & DEEZ NUTS

I forgot to mention that I'm using a 2Tb powered desktop HDD from Seagate & that seems to make a big difference. Spinning platters or not, the 'real world road-tested' results speak for themselves - sorry I don't have a list of numbers & benchmarks for you) Ive got all of my video, music, pictures & backups on the external & only programs and app data on the external. Since doing this everything is a lot faster & stable.. no more bloody "this program is not responding" crap that used to plague me when using Live 9. Cant wait to see how doubling the RAM to 8Gb improves performance aswell..

yes it can run with software, I know that, but it is also a standalone piece that is midi over usb...it doesn't depend on Serato to run, or an OS to run it, the two scenarios are not equal, and if you having problem with your nuts....go see a doc.