I am trying to check that if I buy a new internal HDD it will work in the NAS I am buying. Currently I'm confused about naming schemes and once that is resolved whether there is compatibility. I will gladly author this question to be more general if there is not already an article helping with the confusion of SATA naming and standards. I see similar, but not identical questions and will accept this as a duplicate if thought as such.

The specifications on the eCommerce site for the NAS says, "Controller Interface Type Serial ATA-150", the product home page for the manufacturer says, "Compatible with SATA and SATA II HDD".

The specifications on the eCommerce site for the hard drives say, "Interface Type Serial ATA-300", the product home page for the manufacturer says, "Interface SATA 3.0 Gbps"

Wikipedia says many things about different naming conventions, the closest being, "SATA II 3.0 Gbit/s, which was colloquially referred to as "SATA 3G" [bps] or "SATA 300" [MB/s] since 1.5 Gbit/s SATA I and 1.5 Gbit/s SATA II were referred to as both "SATA 1.5G" [b/s] or "SATA 150" [MB/s]). Therefore, they will operate with negligible differences between them."

Are SATA II and SATA 3.0 Gbps the same? I feel I'm tantalisingly close to getting a definitive answer here before I purchase, but really want to clear up these naming schemes.

  • Quoting from the Wikipedia page. "SATA revision 2.0 (SATA 3 Gbit/s)" So Wikipedia is telling you they're the same. And as far as compatibility between SATA versions The wikipedia page says "The designers of SATA aimed for backward and forward compatibility with future revisions of the SATA standard" – barlop Jun 25 '11 at 16:40

Short answer: yes, they are compatible. And they are "the same thing"--sort of.

SATA II is an official standard, and all SATA II drives and controllers are therefore compatible with each other (assuming they conform to the standard). "SATA 3.0 Gbps" is basically marketing mumbo-jumbo with no "official" meaning behind it. In other words, every company that says they sell "SATA 3.0 Gbps" hardware may be selling slightly different things. However... any device that is marketed as "SATA 3.0 Gbps" is also SATA II--it just has additional "nice" features that go "above and beyond" the bare minimum for SATA II.

So... if you buy a "SATA 3.0 Gbps" device, yes, it will work with your SATA II controllers.

If you buy two "SATA 3" devices from two manufacturers, they may have different feature sets.

Edit: For further clarification, there are 3 Gbps SATA controllers out there, too, and to take full advantage of a 3 Gbps SATA drive, you need a controller with that capability. But any 3 Gbps SATA drive will work in an older SATA controller (at slower speeds) and vice-versa.

Similar confusion arose (and probably still exists to some extent) with SCSI "standards"... many manufacturers sold/sell "SCSI 3" drives, even though there was no official "SCSI 3" standard. It's really confusing, I know...

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  • Thanks for the quick response. You've confirmed what I thought was the likely case (they were compatible, but confusingly named), but I just hadn't read it anywhere. – Johnny Maelstrom Jun 22 '11 at 8:02
  • You've said SATA 3Gbps has additional nice features that vary, and you haven't mentioned any of them. – barlop Jun 25 '11 at 16:36

Actually certain 2nd generation hard drives do not work on first generation controlers (some VIA models) due to a bug/design flaw in the controller.

That is why almost all SATA 3Gbps hard drives have a jumper to limit the interface speed to 1.5Gbps.

There is also a 3rd generation of SATA. Again, the most popular imporovement is the higher interface speed of 6Gbps.

In general, all SATA equipment is compatible with each other. (recently I connected a 2nd generation SATA hard drive to a 10 years old SATA controller - Silicon Image sil3112A - it worked just fine, including hot-plugging)

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  • do the SATA II ones that don't work on SATA I, have a jumper? or the ones that don't work, the small set of SATA II ones that don't have a jumper? – barlop Jun 25 '11 at 16:42
  • "do the SATA II ones that don't work on SATA I" This does not make sense, as the problem is not in the device (like a hard drive), but the controller. For which combinations work, and which not, I don't know. You'll have to google for that. – David Balažic Jun 28 '11 at 13:09

Some update from 2013:

  • Connection of 4 SATA-III harddisks (WD Black 500GB) bought some days ago to an old 3ware 9500S controller works perfectly. But there is no updated Windows driver available for the controller (very, very sad story about this industry, forcing me to throw away one of the most decent RAID controllers ever made is sick). It works in Linux though...

  • Connection of the same HDDs (with the same cables!) to an AMD 790GX based mainboard (in either AHCI or RAID mode) fails: Disks are identified but shown as "Offline" in RaidXpert software OR show I/O errors in Windows event log.

So there are cases when SATA is NOT (downwards) compatible it seems. Still investigating this issue, but should I throw away now the whole PC just because I need a little more HDD space??

BR Florian

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