Is there performance difference for ssd drive connected through usb3 or sata?

Im need to use ssd as external drive (usb3) and like to know if there is some performance overhead using adapter...

(appologizing if this is not the place for this question)


Let's start with the theoretical answer. USB 3.0 has a higher (with SuperSpeed much higher) potential throughput, so it should have a fundamental advantage. However, in most cases the drives you are plugging into USB 3.0 ports are actually SATA drives at heart with an external case and are therefore either translating the data or encapsulating the data for the transmission over the USB 3.0 interface.

Hence, usually you get the SATA limitations with an overhead when using USB 3.0, so even from a theoretical perspective there is no clear winner. This article tested similar drives with the different interfaces and suggests that USB 3.0 was better for reads, but eSATA was the winner for writes. Your mileage may vary depending on your drive and how it manages the translation to USB 3.0 generally (sometimes there really is no way to tell until you test).

In your specific case you are using a SATA based SSD, so basically, yes there will be overhead with a USB adapter (just make sure it is USB 3.0 - eSATA definitely wins over USB 2.0), but you might get as good, or better performance anyway depending on how good the adapter is.


Assuming that SSD internal transfer rates are not the bottleneck, and you mean SATA-III (6Gbps), consider the following:

USB 3.0 raw data rate is 5Gbits/s, which makes it to 500MBytes/s data transfer rate (accounting for 8b/10b encoding). With USB SS link and BOT protocol overhead, the achievable sustainable rate is just about 440-460 MBytes/s.

The SATA-III (6000 Mbits/s) has all the same considerations, so the highest rate goes up to 540-560 MBytes per second.

CONCLUSION: direct connect of SSD to SATA3 port gives better results.

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