[SOLVED] sata question in relation to hard drives

rgs80074

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Oct 28, 2010
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I have a question about the sata speed.


I have a plex server set up. right now every hard drive is on a sata 3 connection but any future hard drive will be forced to go to a sata 2 or I will have to purchase another pci express sata controller.

say after I have the hard drive filled up (not much will change on the drive at that point). how likely is a 3.5" hard drive with up to 64cashe 7200rpm to exceed how fast the sata 2 speed is? and even if it can wuld it make a difference if its not copying but just streaming for the plex server when my internet speed is only 10mbps upload. now when at home on the network I have a gigbyte setup so it could then.

i'm thinking its just a waste of money to purchase another controller card to make them all sata 3 after they've been filled up. the only thing they'd be doing it storing the info until its needed to be streamed.

what are yall's thoughts on this.

ryan
 

4745454b

Titan
Moderator
SATA is just the interface. Think of it as a highway, with the SATA type as the speed limit. SATA I has a limit of 150MBps, (or MPH in the metaphor.) SATA II has 300MBps, etc. The thing is just because the limit is that fast doesn't mean your car/drive will drive/go that fast. How well do your think your 3cyl Geo Metro will do on the autobahn? That Geo Metro isn't going to go 200MPH just because it's driving on a road that allows that speed.

The same is true of harddrives. A drive may support the SATA III spec, but it doesn't mean it's going to max it out. It needs to support SATA III because that's what is found on motherboards now. Spinning drives have only recently gone faster than SATA I spec of 150MBs. While it's been awhile since I last looked, I haven't seen a spinning drive exceed 200MBs, even on the outer edge where it's faster. This means it doesn't exceed even SATA II speeds. You'd be fine to put spinning drives on slower SATA ports. Just because its on SATA III ports doesn't mean you are getting 550+MBps. I can guarantee it isn't going that fast.
 
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4745454b

Titan
Moderator
SATA is just the interface. Think of it as a highway, with the SATA type as the speed limit. SATA I has a limit of 150MBps, (or MPH in the metaphor.) SATA II has 300MBps, etc. The thing is just because the limit is that fast doesn't mean your car/drive will drive/go that fast. How well do your think your 3cyl Geo Metro will do on the autobahn? That Geo Metro isn't going to go 200MPH just because it's driving on a road that allows that speed.

The same is true of harddrives. A drive may support the SATA III spec, but it doesn't mean it's going to max it out. It needs to support SATA III because that's what is found on motherboards now. Spinning drives have only recently gone faster than SATA I spec of 150MBs. While it's been awhile since I last looked, I haven't seen a spinning drive exceed 200MBs, even on the outer edge where it's faster. This means it doesn't exceed even SATA II speeds. You'd be fine to put spinning drives on slower SATA ports. Just because its on SATA III ports doesn't mean you are getting 550+MBps. I can guarantee it isn't going that fast.
 
Reactions: Paperdoc

rgs80074

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Oct 28, 2010
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thats what I was thinking just wanted to confirm it.

and most of the time when copying stuff to the drives (even on sata 3) the really get a sustained transfer rate of 112-150 MB. and once they are full and the system is being used for what its designed for then there would be no more than 15mbps (thats the fastest my internet upload is) being taxed on them.

so I'll just keep the newest drive in the system on sata 3 to to squeak out any extra benefit it can have over the sata 2 and the rest not worry about.
 
I like 4845454b's answer a lot because it is clear and RIGHT. Just added info FYI. The SATA III specs were develped in recognition of the introduction of storage devices with VERY fast data access times - specifically, SSD's. In those, finding and reading the data is entirely an electronic function - there are NO moving mechanical parts - so it is always faster than a classical hard drive. When you access any data on a common hard drive, first of all the head arm has to swing over to the correct track, and then the system starts reading data from the Sectors until the turning disk comes around to just the right Sector it needs. THEN it can actually start reading the data sought. If the data required is not all in consecutive Sectors in the same track, that process has to be repeated for the next chunk of data in that file. Head positioning and disk turning are mechanical functions that require MUCH more time than simply accessing memory "cells" in RAM on an SSD system. The net result is that, as 4845454b has said, there are NO mechanical Hard Drives in existence that can FIND the data as fast as the 300 MBps rate at which a SATA II system can TRANSMIT that data to the mobo. Thus there is NO difference in data transfer speed using mechanical Hard Drives between SATA II and SATA III. ONLY fast SSD's can exceed the SATA II performance specs, and even they cannot reach the max SATA III spec for data transfer. That's by design - the 6 Gbps (600 MBps) max data transfer rate of the COMMUNICATION part of the SATA systems was intended to be MORE that any device that might come onto the market in the reasonable future, so that the communication subsystem would never be the data transfer bottleneck that limits the overall system.
 

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