Tuesday 18 April 2017

StarTech S2510BU3ISO Hard Disk Enclosure with ISO (DVD) Emulation for $20

The StarTech S2510BU3ISO Hard Disk enclosure is similar to the Zalman and IODD enclosures in that it can emulate a USB DVD drive by loading an ISO file.

Note: This product is now discontinued by StarTech and so is unsupported and has bugs (read-on for more details and a workaround for the buggy firmware).
Press the MODE button and the LED changes from HDD to ISO1,
 then press again for ISO2 then again for ISO3 and then back to HDD.

ISO Emulating HDD Enclosures

IODD 2531 $50
Zalman VE350 $45
Startech S2510BU3ISO $23

The StarTech is the cheaper enclosure but is somewhat more limited in it's function however, as it can only emulate one device at a time - either a USB HDD or a USB CD\DVD. Also, it can only emulate CD\DVDs whereas the Zalman/IODDs can emulate disks as well (using VHD or .ima or .RMD files).
The Zalman/IODDs do not need a computer to be available in order to load any one of the ISO files that is on the hard disk, whereas with the StarTech, you can only select one out of three ISOs without needing to connect it to a computer.

For all these enclosures, you simply need to add a SATA 2.5" disk which has been formatted as MBR (not GPT) and with an NTFS file system.

For the StarTech however, you must create three folders, \_ISO1, \_ISO2 and \_ISO3  (not case sensitive) and simply copy ONE .iso file into each of the three folders. Now you can use the MODE button to toggle between USB HDD, ISO1, ISO2 or ISO3.

Rather confusingly, the folders need to be in the form of '_ISO1' - whereas the drive enclosure LEDs are actually labelled as  'ISO_1'. Really sloppy and confusing guys! Does no one do any 'fit-for-use' checks on products these days? - at RM, we always did a full package product fitness-for-use test (FPP FFU) on any new product where we unpacked the final packaged product, went through all the items and documents, and tested the product carefully before we would release it for shipment.

Amazon reviews

Before I purchased the StarTech caddy, I read some Amazon reviews where several people complained that it did not seem to work with some of their hard disks.

So I was prepared for some trouble...

Initial Testing

I first tested it with a 80GB 2.5" spinny disk (Seagate Momentus ST980811AS) which had been recently formatted as simple MBR with a single NTFS partition.

The S2510 seemed to work just fine and I could select any one of the three ISOs.

I started to experiment with different partition arrangements and found:

1. The S2510 firmware search for the first NTFS partition, starting at the first entry in the MBR partition table. So if you have a PTN1=FAT32 and PTN2=NTFS then you should place your \_ISO1 folder in the NTFS volume for it to load the ISOs.

If the partition table is out of sequence, e.g.
Table Entry 1: Start LBA=892345  NTFS
Table Entry 2: Start LBA=2048      NTFS
Then only the partition starting at 892345 is looked at by the S2510 firmware.

2. The partition Type number in the partition table entries (e.g. 07, 0C, 83) is ignored by the firmware. Even if I set the partition type number to 00, the NTFS partition was still seen by the firmware and the ISO was loaded correctly.

3. It is necessary to unplug and re-power the S2510 after adding ISO files. It did not always see the new file when using the MODE button unless this was done. If a different ISO file was placed in one of the folders, unless the S2510 was unplugged & reconnected, it would sometimes still load the previous ISO file! You should, of course, always use the Windows 'Safely Remove Hardware' system tray applet before disconnecting.

4. The Safely Remove applet shows the S2510 in 'hard drive' mode as 'ISO M3', the IdeaPad 300 BIOS shows any of the emulated DVD 'drives' as 'SKY ODD' however sometimes there was not enough time for the StarTech firmware to load the ISO, the IdeaPad BIOS showed the USB device as 'Generic USB Storage' and it would not always boot to the ISO correctly. I had to CTRL-ALT-DEL and get back to the BIOS boot selection screen again to see 'SKY ODD' listed. Sometimes pressing F5 in Windows Explorer was required in order to see the correct label of the newly selected ISO.

5. The StarTech enclosure did not seem to suffer from the 'USB reset' issue which often happens to some other USB devices as an OS boots and loads it's own USB drivers (e.g. Datashur secure pen drives).

6. The current 'MODE' is saved, so that on power-up, the last ISO that was selected is loaded (or HDD mode).

7. If you use Windows Safely Remove Hardware on the S2510, then the MODE button can no longer be used to select an ISO (it just skips over all three!). You must re-connect it before the MODE button will work again.

8. If you add more than one ISO file to the \_ISO1 folder (for example) then it will just pick one of the ISOs (the same one each time). The one it picks may be the first one in the NTFS directory entry???

Testing with other drives

Next, I tried a variety of spinny 2.5" HDDs and also some SSDs (all MBR NTFS). Some worked (i.e. ISO emulation worked) and some did not!

For example: A 500GB Samsung Evo 850 SSD which I had been using as an E2B drive did not seemed to be liked by the S2510 - it failed to find any of the ISOs that I placed in the \_ISO1, \_ISO2 and \_ISO3 folders!

I also found 2 other drives (one Samsung EVO 840 250GB SSD and one Hitachi 5K500.B-250 250GB HDD) which also would not load any of the ISOs.

I decided to re-format the 500GB SSD and re-create the \_ISOx folders + ISO files - I used a 1GB Debian ISO and copied and renamed it, e.g.


This time, the S2510 worked correctly and would load each ISO in turn on each press of the MODE button.

Curiouser and curiouser...

I proceeded to copy about 46GB of assorted files to the 500GB SSD drive and then copy a fresh ISO to the \_ISO3 folder.

Now the S2510 would load ISO1 and ISO2 but not ISO3.

At this point, I suspected that the S2510 firmware was having a problem with the position of the file on the drive. Files below about 47GB position could be loaded by the firmware, but files at LBA 94,286,320 and LBA 102,995,232 could not be loaded by the firmware.

The files were contiguous anyway, but I decided to run Defraggler - Quick Defrag on the drive. This did not move the files, but something had obviously changed because now it would load the ISO that was at 94,286,320! I checked its position and it was still at the same location on the disk.

Note: During further testing, Defraggler failed to 'fix' this problem again, so I don't quite know how it got fixed before!

A reproducible test

I wrote a simple Windows .cmd script to format the drive and then copies 1GB Debian ISO files to the drive, followed by moving the last ISO file to the \_ISO1 folder.

This seemed to show the problem (the S2510 would not load the ISO file). In fact, even if I moved the first ISO file (ISO1.iso) to the \_ISO1 folder, the S2510 would not detect it. Since the ISO1.iso file was near the beginning of the drive, it seems that it is not simply a problem with files that start beyond approx. 46GB.

I have now sent the test script to StarTech support so that they can easily reproduce the issue.


The StarTech S2510 contains a Fujitsu MB86C31 SATA-to-USB chip which apparently has UAS protocol support, but this was not evident in the benchmark results... 

Samsung EVO 850  500GB NTFS

I have an Inateck FE2007 which supports UAS and that gives me about double the sequential speeds with the same SSD drive. Also Device Manager does not list the StarTech under the UASP device tree, so it does not look like the StarTech firmware supports UASP?

Real-world large file copies from an internal SATA SSD to the S2510 ran at about 210MB/s for file writes (using a Haswell-based Asus Z87-A mainboard).


A general purpose, non-UASP, HDD enclosure it was of good build quality (but plastic), a nice sturdy 1 metre USB 3.0 cable with nice, tightly-fitting USB connector. The enclosure had a screwless design and was easy to open and came with a cloth/foam slip-case too.

It is a real shame that the DVD emulation function has this bug. I would often find that, after copying over some files, it would not load a new ISO. This meant I had to reformat the entire drive!

One way around this would be to use two NTFS partitions - keep the first partition as say 30GB and use it only for ISO emulation of the 3 ISOs (so you can format it whenever you like). You can then store all other ISOs, etc. on the second partition and copy them to the first partition when needed.

You would have to use the 2nd partition for E2B files, because adding any files to the first partition may stop the ISO load feature from working at some point!

If I hear back from StarTech about the bug, I will let you know (if you subscribe ;-).

P.S. Weird Windows 1703 bug??

Whilst using the StarTech, I had the following setup:
_ISO1 = Debian ISO
_ISO2 = Kali ISO
_ISO3 = Windows Install ISO

ISO1 and ISO3 worked as expected in Windows Explorer, BUT...
When I selected ISO2 using the MODE button, Explorer still showed the Debian CD volume label but the files were the Kali files! Even if I unplug it and reconnect it to a different Windows 10 system, it still gives me the Debian CD in Explorer!!!
However, a Win 8 system displays the volume label correctly as Kali!
If I actually boot from the StarTech with ISO2 selected, it boots to the Kali menu.
Is this weird or what!!! I think this must be some sort of Windows 10 1703 bug?

Disk Management console in Win10 is buggy!
Drive F: - Who is correct? Disk manager or Explorer ???

Follow Up

For news on the bugs, workaround and support for this device - see this blog post here.

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