what's the point of flashing the raid controller into it mode?

Discussion in 'RAID Controllers and Host Bus Adapters' started by sealand210, May 3, 2013.

  1. sealand210

    sealand210 New Member

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    why don't simply connect all drivers to the mother board? what's the benefit of having an IT mode raid controller? just for the extra sata port?
     
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  2. jtreble

    jtreble Member

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    Initiator-Target (IT) mode provides SAS non-RAID functionality (e.g., for ZFS ...).
     
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    Last edited: May 3, 2013
  3. mrkrad

    mrkrad Well-Known Member

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    Does your motherboard have 16 or 24 sas slots? Most don't.

    HP has the virtual Smart Array for the intel C600 series sata ports (B120i) with 512 FBWC option and HP Virtual Smart Array driver - which works in esxi.
    HP has the virtual smart array for the b320i --> LSI2308 with 512 FBWC (same cache) that sits on the riser. Same Virtual Smart Array Driver.

    You can unplug the riser and the cache will work on the motherboard (!!) but you can't use the intel motherboard sata only ports and the LSI2308 SAS at the same time :(

    The solaris folks do not get a hp Virtual Smart Array driver, so they have to flip the B320i to IT mode and use ZFS software raid.

    With SDS (Software Defined Storage) coming soon, having a ton of reliable SAS ports is going to become seriously important as distributed storage makes ends to SAN/NAS as we know it.

    For example, tweaked sata/sas drivers can ignore SMART and timeouts and just keep on trucking. The QNAP and Synology do this. 180 seconds timeout on a consumer drive? No biggie. 0 seconds timeout on an AV-GP drive (aka no error correction) - that's cool too.

    Intelligent RAID is not so forgiving. A SMART or 8 to 30 second timeout will cause a drive to drop. They usually do not appreciate AV drives which do not have any error correction enabled since that could cause video loss/buffer overflow.

    Perhaps - maybe this will blow your mind. That MSA/P2000 G3 is a SAS Target unix machine and your SAS IT HBA is a very cheap, very fast (4x6gbps) point to point network card.
     
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