5gb/s for a 6gb/s hard drive?

[Boomer112]

Hello!

Hopefully this isn't TOO confusing and i probably should've asked this here, before ordering the LogiLink UA0284 harddrive enclosure thing.
I want to put a harddrive from my old PC into my new PC and to simplify things i thought of getting one of those enclosures that turns an internal harddrive into an external one.

The enclosure i ordered only allows up to 5gb transfer speed (with usb 3.0) and my harddrive has 6gb transfer speed, does this matter in any way that the enclosure is only 1gb slower than the actual harddrive?
I'm guessing the harddrive should still work fine but like, will there be any noticable difference when transfering to/from it or when installing games to it?

I ordered the LogiLink UA0284 for my Western Digital WD10EZEX, to be a little more specific.

[AbydosOne]

1 minute ago, Boomer112 said:

does this matter in any way that the enclosure is only 1gb slower than the actual harddrive?

HDDs can't reach 5Gbps, let alone 6. It won't affect anything. It may show up with an SSD, but it's still plenty fast.

[LAwLz]

Most "high performance" hard drives these days gets at most 200MB/s in sequential benchmarks. The WD black for example tops out at around 160MB/s.

 

That USB connection you got can handle 625 MB/s (5 gigabit = 625 megabytes). 

 

You are nowhere close to saturating the USB connection.

You could probably run 4 high performance (WD Black) hard drives in RAID 0 and still not be bottlenecked by the USB interface. 

[Boomer112]

9 minutes ago, AbydosOne said:

HDDs can't reach 5Gbps, let alone 6. It won't affect anything. It may show up with an SSD, but it's still plenty fast.

Hmm, alright then i guess i've most likely misunderstood something. I guess the ''SATA 6gb/s'' is something completely different then and not the transfer speed? Yeah, uhm i clearly have absolutely no idea what any of this is or means. Thank you, though!

[Boomer112]

6 minutes ago, LAwLz said:

Most "high performance" hard drives these days gets at most 200MB/s in sequential benchmarks. The WD black for example tops out at around 160MB/s.

 

That USB connection you got can handle 625 MB/s (5 gigabit = 625 megabytes). 

 

You are nowhere close to saturating the USB connection.

You could probably run 4 hard drives in RAID 0 and still not be bottlenecked by the USB interface. 

I have absolutely no clue what that RAID 0 means lol, a quick google search made me understand a tiny bit more though. Anyways, i guess everything should be completely fine then? And i shouldn't have to worry about anything?

[AbydosOne]

11 minutes ago, Boomer112 said:

Hmm, alright then i guess i've most likely misunderstood something. I guess the ''SATA 6gb/s'' is something completely different then and not the transfer speed? Yeah, uhm i clearly have absolutely no idea what any of this is or means. Thank you, though!

It's the link rate of the protocol, not necessarily how fast the drive can spit out bits. HDDs cap around 200MBps (i.e. roughly 2Gbps, lowercase 'b'), so the link isn't the bottleneck.

[mariushm]

The hard drive communicates through a SATA interface, which has a maximum bandwidth of 6 gbps - think of the sata interface and cable like a highway.  The "highway" is built in such a way that one could in theory "drive" on it with speeds up to 200 miles an hour (your 6 gbps) , but that doesn't mean cars will actually go up to that speed.

A SSD will be able to achieve up to around 560 MB/s through the SATA interface. Modern hard drive will do up to around 250 MB/s.

 

The USB 3.0 / 3.1 gen 1 / 3.2 gen 1 maximum bandwidth is 5 gbps - this is the maximum number of bits that can be transmitted between a usb device and a usb controller, but it's not the maximum amount of actual data that can be transmitted. The actual data amount is lower, because data has to be transferred in "packets" and each packet has some extra information attached to the packet.

So, maybe 5-10% of the maximum bandwidth is not actually usable.

In practice, you may be able to achieve up to around 4.2-4.5 gbps on USB 5 gbps - that's around 400 MB/s.

[Boomer112]

1 hour ago, AbydosOne said:

It's the link rate of the protocol, not necessarily how fast the drive can spit out bits. HDDs cap around 200MBps (i.e. roughly 2Gbps, lowercase 'b'), so the link isn't the bottleneck.

 

1 hour ago, mariushm said:

The hard drive communicates through a SATA interface, which has a maximum bandwidth of 6 gbps - think of the sata interface and cable like a highway.  The "highway" is built in such a way that one could in theory "drive" on it with speeds up to 200 miles an hour (your 6 gbps) , but that doesn't mean cars will actually go up to that speed.

A SSD will be able to achieve up to around 560 MB/s through the SATA interface. Modern hard drive will do up to around 250 MB/s.

 

The USB 3.0 / 3.1 gen 1 / 3.2 gen 1 maximum bandwidth is 5 gbps - this is the maximum number of bits that can be transmitted between a usb device and a usb controller, but it's not the maximum amount of actual data that can be transmitted. The actual data amount is lower, because data has to be transferred in "packets" and each packet has some extra information attached to the packet.

So, maybe 5-10% of the maximum bandwidth is not actually usable.

In practice, you may be able to achieve up to around 4.2-4.5 gbps on USB 5 gbps - that's around 400 MB/s.

Oohhhh, alright. Thanks for the explanations and clarifications! That's actually really interesting, now that i know more on how it works. Thanks, once again!

[kokosnh]

20 hours ago, LAwLz said:

That USB connection you got can handle 625 MB/s (5 gigabit = 625 megabytes). 

 

SATA III 6Gbps = 750MBps (with 8/10 encoding) = 600MBps real speed. 
USB 3.0 5Gbps = 625MBps (with 8/10 encoding) = 500MBps real speed. 

 

[mariushm]

36 minutes ago, kokosnh said:

SATA III 6Gbps = 750MBps (with 8/10 encoding) = 600MBps real speed. 
USB 3.0 5Gbps = 625MBps (with 8/10 encoding) = 500MBps real speed. 

 

SATA 3 is 6 gbps = 6,000,000,000 bits per second or .  BUT, sata uses 8/10 encoding, meaning for every 8 bits of payload, 2 bits are error checking and correction, so actually only  80% of those bits can be data.

As a coincidence, there's 8 bits in a byte, so if we divide the amount above by 10, we get the actual amount of raw bytes the interface supports : 600,000,000  bytes.

If we use network transfer units where 1 KB = 1000 bytes and 1 MB = 1,000,000 bytes then you have a maximum throughput of 600 MB/s

If we use the units like Windows Explorer shows file sizes where 1 KiB = 1024 Bytes and 1MiB = 1024 KiB then you have a maximum throughout of 572 MiB/s

Because there's overhead - data is transferred through the sata cable in packets, and because there's also control packets mixed with data packets, realistically the maximum amount of data you would be able to transfer is around 560 MiB/s

 

USB 3 is 5 gbps by definition, but has even stricter rules about how data transferred is arranged in packets of fixed sizes, how many packets can be sent, the packets have bigger headers with extra information, so the actual transferred data is significantly lower than 5 gbps - like I said, expect 4.2-4.5 gbps at best.

It's simply NOT possible for a device to saturate the usb 3 bandwidth, the way usb is designed, a hardware device can not arrange data in enough packets to even be able get close to 5 gbps. It's a limitation of the way USB is designed.

 

For somewhat the same reason, even though USB 2.0 was 480 mbps (60 MB/s), you could only get around 35-38 MB/s and the maximum theoretical is 53 MB/s

Maximum payload data packet : 512 bytes

USB 2.0 supports 1 frame per ms, and each frame can contain up to 8 microframes, and each microframe can contain up to 13 packets.

So you have a maximum of : 1000 frames x 8 microframes per frame x 13 packets per microframe x 512 bytes per packet = 53248000 bytes = 53 MB/s

 

Just the same, just because it says 5 gbps at USB 3, you're not ever getting 5 gbps... the way it's design won't allow it.

[kokosnh]

@mariushm  Yeah, I didn't really wanted to get any deeper, than the max media speed. 
I just wanted to clarify the Gbps to MBps conversion and encoding. Because it can be misleading in that form.

Like I don't even want to start with the different encoding in SATA III and SATA express, and the same with the USB 3.2 Gen1x1 5Gbps and USB 3.2 Gen2x1 10Gbps.

And I didn't want to get deeper, because first thing we get is windows MB = MiB, and USB UASP vs BOT.
Then we can go deeper to the storage medium, to MBR vs GPT, then the filesystem, then the cluster size, like no, no, no...