From: ksi@koi8.net
Don Y wrote:
> On 12/11/2025 11:38 PM, Sergey Kubushyn wrote:
>> Don Y wrote:
>>
>> SATA has a slot between power and signal connectors. SAS doesn't have that
>> slot. SATA-only receptacle has a protrusion that goes into that slot. As SAS
>> doesn't have that slot it is not possible to plug a SAS drive into SATA-only
>> receptacle.
>
> Yes, hence the reason you would want a sled to discourage that attempt.
> I.e., let the sled absorb the "interference" and not the connector
> on the drive or backplane.
>
>> The opposite is possible -- SATA drive can be plugged into SAS receptacle so
>> those are SAS/SATA physical connectors.
>
> All of my backplanes are SAS/SATA (though not mix and match). So, I don't
see
> the value of keeping any of the SATA (only!) sleds. I can, of course, use
them
> in the existing backplanes but see no advantage to keeping them over an
> equal number of the SAS/SATA sleds.
Yep, there is no reason unless you have SATA-only device and a box of SAS
drives that you might accidentally plug in there :)
Otherwise there is absolutely no reason for SATA-only stuff.
>> The actual controller that those drives are going to be connected to are
>> separate question. Many SAS controllers will also work with SATA drives. The
>> opposite is not true.
>
> Yes. The extra/augmented interface is not present on the SATA drives so
> not present on a SATA-only backplane.
>
>> AFAIK there are no reliably working USB<->SAS docking
>> stations. There are _SOME_ that claim to be SAS but those are hit and miss
--
>> it is impossible to tell if they'll work with a particular drive. SATA<->USB
>> ones are aplenty, cheaper than dirt, and almost all of them work.
>
> I've not looked for a SAS dock as I can just pull a drive out and slap a
> new/temporary drive in its place just as easily as putting one in a dock.
> Especially as the backplanes tend to support higher bandwidths than the
> docks.
It is not all that straightforward if ALL your drives are in a hardware RAID
of some kind...
>
>> Another issue is that SAS drives don't always have power of two sized
>> sectors. Although many are usual 512-bytes per sector there are still many
>> with 520/528/536 etc. bytes sectors. Many of them (but not all) can be
>> re-formatted to 512-byte sectors but it is not for the faint of heart :)
>
> I've also encountered "12V only" drives.
>
> I've not had problems *using* the SAS (or SATA) drives. Just wondering which
> sleds have value to keep (this is the time of year I upgrade my tools)
>
>> SAS is SCSI with serial physical interface, akin to PCIe that is PCI with
>> serial physical interface. SATA is, eh, ATA with serial physical interface
>> so it is totally different device.
>
> SAS also allows FDX communication instead of SIMPLEX and a fatter pipe.
>
> And, of course, tend to be more durable than SATA.
SCSI are better in any respect, just more expensive and require different,
more expensive controllers.
> So, can you see any reason other than "inhibiting mating" for there to be
> two types of sleds? (the sleds look like swiss cheese with all the
> various mounting holes supported)
It is the ONLY reason behind having SATA-only sleds/connectors.
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