I have a StarTech PEXUSB3S4 USB 3.0 host adapter on Win7 SP1 64bit AMD/ASUS.

Recently, when mirroring (large recorded TV files) from internal SATA HDD to new PNY and HP 128GB & 256GB USB 3.0 flash drives. The copying process using ZTreeWin was painfully slow (more like USB 2.0 speeds) whereas it had previously been fast on the same kind of USB 3.0 flash drives.

Same problem whether ZTtreeW64 v2.2.19 or v2.4.145.

Windows shows the new USB drives format as FAT32, which I assume is really exFAT.
-- Whereas the old drives I had reformatted NTFS --.

I won't bore you with drive speed utility stats, but they show the exFAT drives as performing at USB 3.0 speeds comparable to the NTFS drives.

I finally concluded the dramatic speed difference using ZtreeWin is between the USB 3.0 drives that I had reformatted NTFS, and the new ones still in exFAT format.

So,
- I ran speed test on a brand new exFAT 256GB 3.0 flash drive: results positive.
- I copied a few gigabytes with Windows Explorer: the writes occur at USB 3.0 speeds.
- I copied a few gigabytes with ZTtreeWin: the writes are very very slow.
Next,
- I reformatted the same USB drive NTFS (quick format, default parameters).
- I ran speed test again on the flash drive: results positive.
- I copied a few gigabytes with Windows Explorer: the writes occur at USB 3.0 speeds.
- I copied a few gigabytes with ZTtreeWin: the writes occur at USB 3.0 speeds.

I searched this forumn and ZTWiki for exFAT and found nothing about this. Am I alone in having this problem?

Sincerely yours,
R.