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Information about SATA interface.

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February 8, 2010 10:05:23 PM

I would like to ask some quick questions that have been bothering me, since i intend of building a new server pc with lots of drives focusing on SATA. Well here goes.

A)Is it possible to add/remove drives from internal SATA connectors? I plan on having an open case and I'm wondering whether this could really be an issue.

B)Concerning eSATA, does it behave the same way as USB? If i connect an HDD using eSATA will i get the same tray notification, found new hardware/installing new hardware and then have to safely remove it, or will i have none of that?

C)What is the real speed of sata150/300? I'm talking about a realistic speed not the nominal of 1.5/3.0 Gbps

D)Will it be wise to wait for the SATA3 protocol? Most of my drives are already sata2, so i will also have to wait and buy sata3 drives, so that's an issue as well, even if i manage to get a mobo with sata3.
a b G Storage
February 9, 2010 5:59:19 PM

SATA 3 will only be usable, real world, by SSDs. Normal platter drives can't even use all of the SATA 2 speeds.
a c 328 G Storage
February 9, 2010 6:21:50 PM

A) It MAY be possible to "hot swap", which is what you seem to ask. That feature is NOT part of the SATA specs, but it IS part of true eSATA, and sometimes mobo makers have added this feature to internal SATA controller functions. But trying to verify for sure can be tough. HOWEVER, if you don't plan to really "hot swap" - that is, disconnect, remove, and reconnect SATA drives while actually in use with power on - but intend only to disconnect / reconnect when power is OFF, then no problem, of course. But why? If you really plan to have many drive units that must be removable and then may be re-inserted, think about a system that mounts each drive in a "caddy" and has a front-of-case mounting system for inserting and removing removable drives. Such a system will come with drivers to ensure clean hot swapping. Not cheap.

B) eSATA DOES have full support for Hot Swapping as part of its specs, so yes you should get all those notifications. Note, however, that true eSATA is faster than USB2.

C) Long-term average data transfer rate with SATA I have seen in test reports range from 40 to100 MB/s - newest test results tend to be in the higher end of that range. The 150 / 300 numbers are the MAX BURST rate, not the average sustained rate. Given that, even your older original SATA units may be fast enough to keep up with the rest. USB2, typically, tops out closer to 30 MB/s

D) For lots of reasons inherent in HDD units, it will be VERY difficult to get close to the current SATA II Max Burst Rate on sustained average performance, so the newest SATA 6.0 Gb/s spec will never be achieved there. It DOES make sense, though, for the newest SSD's.

Don't know exactly what you are building. But some large servers with multiple drives are built with dedicated drive cases and use things like RAID5 or RAID6 with hot swapping capabilities so that the storage subsystem never is really down, even if a drive fails. This requires more advanced management of the RAID system itself, and uses hot swap capabilities, but not via the recent eSATA standard.
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a b G Storage
February 9, 2010 10:47:07 PM

Paperdoc has it right except for one thing. Sata 3.0Gbit with AHCI enabled does support hot-swapping.
a c 328 G Storage
February 10, 2010 12:47:14 PM

cjl is right, and maybe I caused confusion. The formal SATA spec does NOT support Hot Swapping, whereas the eSATA spec does. Some SATA controllers in mobo chipsets also include this even though it is not required in SATA, just so you can use their hardware with a simple adapter plate that comes with external enclosures to convert that SATA port to behave like a true eSATA port. I would assume that any chipset maker that does this also will ensure the support is included in the driver they supply for the mobo devices. BUT the problem is that it is extremely difficult to get that "in writing", so I would not rely on having Hot Swap in ANY plain SATA port.
February 10, 2010 8:46:46 PM

Ok so allow me to collect my thoughts.

SATA3 should be useless so to speak for 7200 hard drives. Possibly 10-15k raptors and SSD should be able to take advantage of that, so as far as i'm conerned for my file management and server needs i will not beneift.

What about USB3.0? IT hasn't come out strongly yet, but what d'ya reckon? Supposedly it supports up to 3.2 gbits which is something a little bit over sata2.

Will i be able to take adantage of this and use internal sata2 drives with certain cable transformers or external enclosures and output data via usb3.0?

Thing is, that external hard drives and external enclosures are either cheap and support usb 2.0 or are a bit expensive and support esata and gigabit lan.

So using external drives to store data either forces me to fill in the system with usb2.0 drives which get miserable 10-20MB speeds, or pay for esata controllers since mobos come only with 1-2 on-board. Gigabit is not so good either since you get almost half (500MBPS) according to testimonials which makes something slightly better than usb 2.0.

So what's my best bet here, when i want to add internal hard drives and achieve satisfactory speeds and overall performance?

BTW i only asked about hot-swapping since i intend to build a SOHO with an open case (Antec skeleton) and connect internal drives on the mobos internal ports.

And since most of them have a 4-6 port limit, i may have to disconnect-reconnect any additional drive i may want to manage.
a c 328 G Storage
February 11, 2010 2:18:42 PM

USB is normally used for an EXTERNAL interface - nobody uses it internally as a HDD connection system. So you won't find internal HDD units to connect to internal USB3 ports when they come out. As you anticipate, the only way would be to adapt a SATA II drive to a USB3 interface. I REALLY doubt that would get you any advantage, for two reasons. Firstly and most importantly, the reason SATA II drives do not currently achieve their maximum speeds is NOT the interface - it is the limits of the mechanical drive design inside, and changing to a faster (max speed) interface will not change that at all. That is why the new SATA 6Gb/s system does not hold any promise for faster performance on traditional hard drives, but DOES show real speed for Solid State Drives. Secondly, any enclosure or adapter that connects a SATA II drive to a computer using a USB interface must do a data "translation" - SATA to USB at the enclosure / adapter - before sending it, and that is a slight delay in every data transfer. This is just one of the factors that make eSATA enclosure systems much faster than USB - eSATA has NO such "data translation" step, because it is just a very slightly modified SATA system.

You can buy mobos now with 6 (a few with 8) SATA II ports built in. For example with 8 SATA II ports, see here for AMD-chip mobos:
http://www.newegg.com/Product/ProductList.aspx?Submit=E...

and here for Intel chip-based
http://www.newegg.com/Product/ProductList.aspx?Submit=E...
I even saw some Intel-based board with 10 SATA ports.

Then you need a case large enough to allow mounting all those, and a suitable power supply. How many drives were you planning to use, anyway? Even if you go with RAID5 managed by on-board RAID, a 5-disk array can give you 80% of the total drive capacity. So 5 disks of 2 TB capacity gets you 8 TB of usable space. A 10-port mobo could allow up to 16 TB. Need more? Or, if you want to go to RAID6 you might get only 8 TB out of 6 disks on an 8-port mobo IF you can find a mobo with that RAID level built in. I'd bet, though, that going that far will put you into dedicated add-on RAID controller cards, like these big-$ babies (one even gives you 12 SATA II connections for two RAID6 arrays!):
http://www.newegg.com/Product/ProductList.aspx?Submit=E...

If you are going that far, I hope you are a very experienced network and server administrator.
February 11, 2010 4:09:45 PM

1793658,8,121166 said:
USB is normally used for an EXTERNAL interface - nobody uses it internally as a HDD connection system. So you won't find internal HDD units to connect to internal USB3 ports when they come out. As you anticipate, the only way would be to adapt a SATA II drive to a USB3 interface. I REALLY doubt that would get you any advantage, for two reasons. Firstly and most importantly, the reason SATA II drives do not currently achieve their maximum speeds is NOT the interface - it is the limits of the mechanical drive design inside, and changing to a faster (max speed) interface will not change that at all. That is why the new SATA 6Gb/s system does not hold any promise for faster performance on traditional hard drives, but DOES show real speed for Solid State Drives. Secondly, any enclosure or adapter that connects a SATA II drive to a computer using a USB interface must do a data "translation" - SATA to USB at the enclosure / adapter - before sending it, and that is a slight delay in every data transfer. This is just one of the factors that make eSATA enclosure systems much faster than USB - eSATA has NO such "data translation" step, because it is just a very slightly modified SATA system.

Ok so what i'm getting from this part, is that to go from sata to usb a translation process has to take place in order for the data to be pushed through. That of course is understandable and explains part of the delay happening. So cables that allow you to do this, have micro-processors and ALU in order to achieve this? I have been using this method for a while but speeds are terrible. I have only been doing it so that i can transfer data from my main drives to the larger capacity drives, so that i can free-up space on my main drives. I just wonder if usb3.0 would make a differnce minding not the initial translation needing to happen.

Quote:
USB - eSATA has NO such "data translation" step, because it is just a very slightly modified SATA system.

You can buy mobos now with 6 (a few with 8) SATA II ports built in. For example with 8 SATA II ports, see here for AMD-chip mobos:
http://www.newegg.com/Product/ProductList.aspx?Submit=E...

and here for Intel chip-based
http://www.newegg.com/Product/ProductList.aspx?Submit=E...
I even saw some Intel-based board with 10 SATA ports.


Be it 6 or 8 or even 10 makes it finite. I'm desperately looking for a solution that will allow me to add more drive as i go, not having to worry each time, if there's a free slot, and what i have to do to obtain one.

So far i have 8 internal disks used externally for storing downloaded files, 3 more internal disks for os installations and 5 external drives (USB2.0 interface), and i want to be able to keep adding more without needing to worry.

Quote:
Then you need a case large enough to allow mounting all those, and a suitable power supply. How many drives were you planning to use, anyway? Even if you go with RAID5 managed by on-board RAID, a 5-disk array can give you 80% of the total drive capacity. So 5 disks of 2 TB capacity gets you 8 TB of usable space. A 10-port mobo could allow up to 16 TB. Need more? Or, if you want to go to RAID6 you might get only 8 TB out of 6 disks on an 8-port mobo IF you can find a mobo with that RAID level built in. I'd bet, though, that going that far will put you into dedicated add-on RAID controller cards, like these big-$ babies (one even gives you 12 SATA II connections for two RAID6 arrays!):
http://www.newegg.com/Product/Prod [...] rchInDesc=


Actually i plan to go open case, antec skeleton or antec skeleton mini, and have external mobile racks for mounting/connecting the hard drives, so that i wont have to open case each time and hassle.

This is one such example.

http://www.e-shop.gr/show_per.phtml?id=PER.700547&u=LIA...

I bought it like 2 years ago when i planned on getting one of these big server cases full of 5.25 slots (later decided not to, and got left with the rack!).

Basically it allows 4 3.5" HDD's and has an internal lian li fan for cooling off the drives.

As for the cable i'm thinking of converting the internal Sata ports to esata and then connect from the sata interface of the drive to the esata port. Another thought, is having a slightly longer sata cable running from the case straight to the drive. But it has to stay always hooked on the motherboard side, and connect to each drive i might want to swap.

As for RAID i really dont need to bother. It's just downloadable content, so even if a drive fails, well tough luck. I just want to be able to take advantage of the 100% of the drives capacity.

Quote:
If you are going that far, I hope you are a very experienced network and server administrator.


I;m just a "fanboy", there's no administrator here :) 
[/quote]
a c 328 G Storage
February 11, 2010 8:18:38 PM

One way to get "unlimited" drive spaces might be to go to NAS - Network Attached Storage - modules in which you have little more than several drives with controllers and power supply, and an ethernet port to make the entire unit an accessible storage device on the network, shared by all computers. There are security issues here, but known solutions. You COULD get to a limit that there are only 26 letters in the naming alphabet, of which about three already are "used". But if it can be set up so that each NAS unit behaves as ONE drive (composed of several to get big capacity), maybe that can work. I don't know nearly enough about these systems to say for sure.
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