On Jun 17, 2013, at 7:12 AM, Sebastian Gabler <[email protected]> wrote:
> Hi, > > it occured to me that obviously some ZFS Storage systems only feature a > single SAS HBA, including the ZFSSA 7320. At least, as far as I understand. > From what I saw in the 7320 documentation, each of the two HBA ports is > connected to each of the two ports of a shelf, which should protect from the > failure of a single cable, SAS Expander or drive controller (using dual > ported drives). My understanding is that this topology is drawing upon > MultiPath. But that still should make the HBA a SPOF, shouldn't it? As HBAs > are a quite cheap commodity, I wonder why I even don't see a secondary HBA as > an option for SUN ZFSSAs, or other appliances like the Netgear ReadyNas. > > Thanks for any hints on how to exclude the HBA as a SPOF without using a > cluster. If you go one step further, these systems usually have a SPOF at the IOH. For more recent Intel processors, the IOH is integrated onto the CPU, which is also a SPOF. You can't get full redundancy with those systems, you have to move up to a SPARC or Power based system. In short, it can become a simple economic decision rather than a RAS decision -- adding another HBA does little to increase the overall availability but does add costs. There are mathematical models that can be used to evaluate the impact of these decisions. -- richard -- [email protected] +1-760-896-4422 _______________________________________________ OpenIndiana-discuss mailing list [email protected] http://openindiana.org/mailman/listinfo/openindiana-discuss
