SATA II disk and drivers: worth it?

[kernel64]

I was thinking of making SATA drivers part of my OS from the very beginning, and spending some cash on getting a SATA II disk with a 16MB cache, specifically a Seagate 300GB SATA II 7200.10 16MB cache disk. Is it worth it? Are SATA disks all they are hyped up to be? Has anyone had any experience writing drivers for SATA disks?

Thanks...

[Cody]

Well, I believe that depends upon how you use the disk. If your application is disk centralized such as web server your sata II will be superior to common ATA IDE or Scsi disk. But you may not notice the difference otherwise.

[Solar]

For me the main advantage of SATA is that its cables are so much easier to thread through your tower casing.

But I'm someone who until recently was quite happy with a 1999 laptop, so your mileage regarding what is acceptable and what is good performance might vary.

[Cody]

You may feel even more convenient when SATA II evolves to hot-pluggable comparable to its USB peers. They have already been pushing on this.

[Solar]

Nevermind. Even my old laptop had a 400 MBit firewire connector - plenty fast enough for me.

[kernel64]

Thanks for your replies. Is SATA II really noticably faster? I am sceptical of the 3Gb/s figure touted for them. That must be burst, not sustained. If it was sustained, hell yeah, yummy... ;D I can't find any average seek times however, like I can with PATA disks. I would imagine they are much the same, since internally they are identical. An arm with read/write heads and a platter. Only the host controller is different.

Certainly the disk is a big bottleneck in system performance for nearly everyone except those who just do word processing and surfing the web or whatever. But I like to do big compile runs so memory and disk is important for me.

Would be nice if I could know in advance if it's going to work with my OSes... I've heard some horror stories about SATA, although if Hale Landis' site is anything to go by, that is quite probably due to non-shielded cabling as much as it could be a driver issue because of the competing standards.

On the whole, since Hale wrote his page on SATA back in late 2003, things must have improved with SATA and SATA II looks promising...

[Pyr0Mathic]

This might be a bit off topic, but my main-board has the function to enable you to make from a Sata drive an IDE drive so then you wouldnt need to build the SATA driver, just a universal PATA/IDE driver would work, but i dont think you then have the 300MB/s which SATA II offers you.

Regards
PyroMathic

[Solar]

At the end of the day you'll be limited by how fast the read/write heads of the hard drive can get the data off the spinning disks, and there the top of the scale is somewhere around 70 MByte/sec currently - for SAS-disks turning at 15k RPM. ATA disks (with 7200 RPM) are somewhere in the 50-60 MByte/sec range.

Add to that some access latency (getting head and sector together).

Bottom line, don't confuse interface speed with what the physical drive is capable of giving you. You might have a 800 Mbit/sec. firewire or a 350 MByte/sec SATA II interface, but when you're running a single hard drive, even ATA/100 is enough.

[kernel64]

Thanks for the info Solar. Since motherboards with SATA II are so much more expensive, I don't think I'll bother. And there are plenty of boards with SATA I, but not many SATA I disks to go with them (only 40GB or 80GB disks at my shop)! Weird.

[JoeKayzA]

It should be mentioned as well, however, that you _can_ achieve the maximum interface speed for transfers from disk-cache.

[kernel64]

That's interesting because the new SATA II disks have caches up to 16MB in size. Typically homebrew OSes are small systems and could conceivably have a great deal of their on-disk stuff in the cache most of the time.

[Solar]

The numbers I quoted - 50-60 MByte/sec. - are values measured in real life, i.e. including the effect of the cache, smart read-ahead logic and everything.

[Candy]

Thanks for the info Solar. Since motherboards with SATA II are so much more expensive, I don't think I'll bother. And there are plenty of boards with SATA I, but not many SATA I disks to go with them (only 40GB or 80GB disks at my shop)! Weird.

I've recently taken a dive into this stuff (since I was buying a new computer myself - it's 6 days old now, so according to weird al it's obsolete) so this might help:

Mainboards with SATA-II needn't be very expensive, I've got a mainboard of 70 euro with 4 SATA-II ports. It's an Asrock mainboard, which you might not prefer. It has a pretty weird thing onboard that allows two to be extended to the rear, so you can attach external SATA/II disks.

The 3Gb/s number is correct, but pretty pointless. Due to overhead on byte-transmission on a bit-channel, it reduces to 300MB/s instantly, which is then used for whatever your harddisk can make of it. I've got a 250GB Samsung SATA-II disk which performs pretty nicely, believe it makes between 60 and 70 MB/s practical serial speed and due to NCQ (native command queueing) up to 12MB/s in common Windows usage (which a local computer magazine tested for me - I didn't influence it).

You can use any SATA/II disk (at least most, my disk has it) in SATA/I systems, they have a "reduce function set" jumper. The mainboard booklet included information to do so on 2 or 3 brands of disk, so I expect most to have it.

Writing a driver is either easy & cheating or hard. You put it in IDE emulation mode and accept all limitations or you write a true SATA driver. I'll post something about it on the forum when I get to writing one. You can send me anything to test on this machine and I'll test it. I recall the SATA controller is in AHCI mode, but I'm not sure.

Thinking of it, I didn't even buy the mainboard for the SATA/II interface but more because of the PCI-E lanes and the memory. You don't need SATA/II for any practical reason anytime soon.

[bubach]

it's 6 days old now, so according to weird al it's obsolete

His music is really cool.

[Cody]

Writing a driver is either easy & cheating or hard. You put it in IDE emulation mode and accept all limitations or you write a true SATA driver. I'll post something about it on the forum when I get to writing one. You can send me anything to test on this machine and I'll test it. I recall the SATA controller is in AHCI mode, but I'm not sure.

Thinking of it, I didn't even buy the mainboard for the SATA/II interface but more because of the PCI-E lanes and the memory. You don't need SATA/II for any practical reason anytime soon.

The SATA controller on board today can be either in compatible mode or AHCI mode. AHCI provides a better programming interface than traditional Task file register which also help to boost its performance.

We did our own SATA/AHCI driver in bios phase, windows has come out with its own SATA driver already but so far they haven't deployed it. You need to press F6 during installation so as to inject your 3rd party drivers. And AFAIK, linux has already had SATA drivers but the FC4 I use still didn't support installnation or boot from SATA disk.