Sata 3.0gb/s Really Seen?

[robAP]

im just looking at the types of drives and the types of supported connections on motherboards and everyones selling 3.0 speed drives. in theory they should transfer that much data....well, are we really seeing 3.0gb/s transfer speeds out of a single drive?? or are we barely above the older 1.5? is there a loss in hooking up a 3.0 drive to a 1.5 connection on the board? by how much? currious about just the normal single drive but in a raid array is this further compromised or is it just the same transfer loss?

[coolcat97]

This question bothered me also... 7,200 RPM drive = SATA II, 15,000 RPM = SATA II... that makes sense... NOT

[ir_cow]

if you dont have raid 1 your not going to see 3.0gb/s being fully used, most drives (aka any 7,200rpm) cant even do 1.5gb/s. what is good about 3.0 is the clip on the connectors so the cord doesnt fall out (it keeps happening to me when i move my computer). so unless you have some kind of raid or a raptor drive just see it as a marketing thing.

 

 

 

go check out "HD Tech" and benchmark your drive

[Verran]

I've wondered about this myself.

 

If my math is correct, then 3Gb = 375MB. 375MB/s seems like an aweful lot for a hard drive bus, especially when you figure that it's serial, and not parallel like the old IDE drives. To me, even 1.5Gb (188MB/s) seems like supreme overkill for the sustained data speed of a hard disk. Last time I did the research, the sustained data speed of a standard 7200RPM disk was around 40MB/s. I'm sure it's gone up since then, but I'd be willing to venture that it hasn't quintupled.

 

One possible benefit is that the faster bus will benefit data transactions that are still in the disk's cache. With new disks having 16MB of cache (1TB reportedly having 32MB in some cases), this could prove to be worth it. Cache transactions wouldn't be subject to the incredibly slow (relatively) platter access, so they could make more use of the bus. There's also burst data rates, but those seem a little too "ideal" for me to really weigh them heavily in my purchasing choices.

 

Also, the 3.0 features more than just the bus speed. It also provides features like NCQ, which seem to show noticable speed increases. The SATA page over on Wiki lists a surprising amount of improvements in the protocol with 3.0.

 

As for using a 3.0 disk on a 1.5 board, I have never heard of people having issues really. SATA seems to down-step pretty gracefully in either case (slower disk, or slower board). But really, with the practically invisible price difference between 3.0 and 1.5 disks, I think it's only really a factor for slower disks that someone already has and wants to put to use.

[coolcat97]

I thought 1024 MB = 1 GB .... so ... 3072 MB = 3 GB... Right?

[Verran]

I thought 1024 MB = 1 GB .... so ... 3072 MB = 3 GB... Right?

You're right, but that's not the issue at hand.

 

You'll notice that the 'b' in 3.0Gb/s is lowercase, while the 'b' in 375MB is uppercase. That's because (like many data rates, such as 10/100 networking), the speeds are rated in bits, not bytes. There are 8 bits in one byte. So dividing the 3.0Gb by 8 gives the speed in bytes, which is what most people are familiar with.

 

'B' is commonly used for bytes, 'b' is commonly used for bits.

[coolcat97]

Ah, thanks for the clear up. I did not know of the GB \ Gb difference.

[hardnrg]

the main difference that you will find is that SATA2 drives are generally faster just because they are newer models, not because of the interface... also the NCQ feature made available with SATA2 can help for high loads of random access... so SATA2 with NCQ drives can be faster than similar SATA1 drives...

 

a single drive will not saturate the bandwidth of SATA1 or SATA2... two extremely fast drives in RAID-0 may be borderline saturation at the start of the disks for SATA1, so there may be a very slight aleviation of a limit from SATA1 to SATA2 in this situation

 

RAID-0 volumes consisting of three or more drives would certainly saturate SATA1 bandwidth and then SATA2 really pays off...

 

everyones selling 3.0 speed drives. in theory they should transfer that much data....well, are we really seeing 3.0gb/s transfer speeds out of a single drive??

 

the drives aren't rated for 3.0 Gbps, they are SATA2 drives, and SATA2 has a total bandwidth of 3.0 Gbps... it's not a speed rating or capability of the drives, it's a total speed limit of the data bus

[robAP]

thanks Nrg and Verran for clearing that one up. so the drive wouldn't be able to output that bandwith but i wonder what raid combinations of what drives would output such a data stream? by your account, lets say two 10k raptors in raid0 would come close to a 3.0 saturation, but a pair of normal 7200 drives in raid-5 would probably only hit the 1.5 limit and just barely it sounds like. ill have to go get benchmarks of segate's newer parallel drives and see what the ultimate outputs (normal and burst) would be of a pair in raid-0.

 

yeah i was considering my server build using a nice raid-5 of terrabyte space. (3x500's) but those drives are the shiny new new segate parallel drives. the board i have for this job now could do it but it only has the SATA-I headers and i was thinking about exactly that. would i be silly for doing such a thing or not and would i be saturating this skt.A board. (its a home server, not an encoding machine) i am thinking tho about just going with a SATA-II and raid-5 capable board instead just so everything is nicely matched like a pair of blue socks. if i do this, i would have to buy a nice C2D board/chip/mem/ and move my current parts over to 2nd status...and thats $400 more. (i am looking for an excuse to use my new 1kw nzxt psu on something.....and move my 535 enermax to the server.)

 

edit: well S***. upon further stats checking, the board only handles raid-0 and 1. so much for my 5 idea. i could do a poor mans raid 5 and do a raid-1 but that would be seriously slow. i guess ill have to go get the newer stuff then....crap....(it would be my last build for probably 3 years+)..

Edited June 20, 2007 by robAP

[hardnrg]

by your account, lets say two 10k raptors in raid0 would come close to a 3.0 saturation, but a pair of normal 7200 drives in raid-5 would probably only hit the 1.5 limit and just barely it sounds like.

the maximum data throughput of SATA1 is ~150MB/s... so that would be 75MB/s for two drives in RAID-0... this is fast, but possible at the beginning of the disk for high performance drives... I think my SATA2 Hitachi's start out around 80-90MB/s right at the start of the disk

 

also... I'm wearing blue socks

[romeo55]

It depends on what you mean.

 

A few drives using a SATA2 interface in RAID-0 can hit 300MB/s+ for a very short time, but it can only sustain something like 120MB/s-140MB/s. Even if you have 8 drives running in RAID-0, it'll never hit the 300MB/s mark, not even the 160MB/s mark.

 

Manufacturers tend to rate on maximum throughput no matter if it's misleading. DVD drives, rated for up to 16X, in reality, never really hits that mark, hovers around the 12x-14x mark.

Edited June 20, 2007 by The Unforgivin

[robAP]

well i took a trip over to storgereview.com and went through their database. you can select all kinds of measurement and sort all the drives out and find out whose fastest, or most, etc. i would sugget anyone concerned with any bandwith limitations should check it out.

 

according to this, the drives with the fastest minimum read transfer rate are of course the scsi 15k drives. ($$bling bling)

but check out this link here: http://www.storagereview.com/php/benchmark/bench_sort.php

thats the sorted list of whose fastest in minimum transfer rate (normal reading not burst)

so for example the drives im looking at are good fast SASA-II drives. nothing crazy fancy just good. what did i find inthis list?

 

segate barracude ES sereis drive w/NCQ= 44.3gb/s minimum transfer, 78.5gb/s burst. so in a raid-0, 157gb/s burst and 88.6 minimum. i remember my old raid-0 array of WD 80 gig sata-I drives put up a near 90 minimum transfer number so this would fall in line with that as well. but if i went to a pair of raid-0 raptor 10k wd150 drives, they would in theory show 176.6gb/s burst and 120.4 minimum/normal transfer rates. so the only real reason to have a 3.0gb/s board is to handle burst reads of RAID arrays using fast drives....the only wawy to overload the bus is to use expensive fast drives in a server environment or greater.

 

who has that at home? and why would i need 10k high burst drives in my home server? i dont.....ijust need raid-5 who cares about the transfer at this point.

 

thanks everyone for helping me find this out. sometimes i just have to talk/type through something.