On Tue, Apr 16, 2013 at 5:49 PM, Jim Klimov <[email protected]> wrote:
> On 2013-04-17 02:10, Jay Heyl wrote: > >> Not to get into bickering about semantics, but I asked, "Or am I wrong >> about reads being issued in parallel to all the mirrors in the array?", to >> which you replied, "Yes, in normal case... this assumption is wrong... but >> reads should be in parallel." (Ellipses intended for clarity, not argument >> munging.) If reads are in parallel, then it seems as though my assumption >> is correct. I realize the system will discard data from all but the first >> reads and that using only the first response can improve performance, but >> in terms of number of IOPs, which is where I intended to go with this, it >> seems to me the mirrored system will have at least as many if not more >> than >> the raid-zn system. >> >> Or have I completely misunderstood what you intended to say? >> > > Um, right... I got torn between several letters and forgot the details > of one. So, here's what I replied to with poor wording - *I thought you > meant* "A single read request from a program would be redirected as a > series of parallel requests to mirror components asking for the same > data, whichever one answers first" - this is no, the "wrong" in my > reply. Unless the first device to answer returns garbage (something > that doesn't match the expected checksum), other copies are not read > as part of this request. > Ah, that makes much more sense. Thanks for the clarification. Now that you put it that way I have to wonder how I ever came under the impression it was any other way. _______________________________________________ OpenIndiana-discuss mailing list [email protected] http://openindiana.org/mailman/listinfo/openindiana-discuss
