Toshiba RM5 Value SAS Adopted by Dell EMC

Discussion in 'STH Main Site Posts' started by Cliff Robinson, May 3, 2019.

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  2. zir_blazer

    zir_blazer Active Member

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    For some unexplained reason I have a fetish with SAS. Given the fact that there is a high degree of compatibility between SATA and SAS, I don't know why since the Intel X79/C606 Chipset neither Intel nor AMD tried to integrate a HBA SAS Controller as replacement for the standard SATA one, even if it was just to plug SAS disks in a basic way. Actually, since Intel tried to do so but it lasted just a single generation, I wonder what failed... Are basic HBA SAS Controllers that much more complex over SATA/AHCI ones?

    For AMD Rome it would be wonderful if now that the SERDES was upgraded to support PCIe 4.0 and USB 3.1 10 GBps, it could also do SAS3 instead of just plain SATA3. Alas, given the fact that is rare that someone uses the built in 10G NIC, one has to wonder that if AMD spended time to include SAS support, if anyone is ever going to use it.
     
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  3. ATS

    ATS Member

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    It is primarily because customers and vendors have standardized on specific controllers and controller eco systems along with associated firmware. Know of multiple cases where large orgs have basically used bespoke firmware because V1.1x of the firmware worked but has an esoteric bug (security or otherwise) that got fixed in V1.2 but other changes in V1.2 caused issues.

    SATA is pretty simple and people only really expect it to work point to point while with SAS they have an expectation that it works with a large ecosystem that has various levels of compatibility. SATA in some ways has the advantage that regardless of what the paper spec is, the real spec is that it works with Intel's SATA controller (in many ways hardware based specs are stricter and open to less interpretation than paper specs). SAS however really never had that level of dominance from a single vendor and in addition has significantly more functionality which makes overall long term interop a much more complicated picture (as just one example look at the various issues wrt SAS expander compatibility, in theory any expander should work with any controller, practice not so much).

    Luckily the days are likely numbered for both (SAS and SATA) and PCIe (and hence NVMe) have much more robust interop requirements and testing so this should all eventually go away.
     
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  4. croakz

    croakz Active Member

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    SAS over SATA adoption usually isn't about what controller a manufacturer puts in, but the cost of the drive. The RM5 is an example of that, make it a good value (and cheap enough) and they'll move to it.
     
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