Re: freebsd-performance Digest, Vol 4, Issue 7

From: Petri Helenius (pete_at_he.iki.fi)
Date: 06/19/03

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    To: "Jin Guojun [DSD]" <j_guojun@lbl.gov>
Date: Thu, 19 Jun 2003 09:57:35 +0300

    > But this seems to have different problem. At least write to RAID 1 requires
    > twice bus bandwidth for soft RAID 1. So, read should be faster than write.
    > But current read is 67 MB/s, write is 10 MB/s. Something is not working.

    Might be that whatever youīre using for the write waits for the second write
    to complete before it issues a write on the first drive again. vinum does this,
    it does not dispatch both writes at the same time. (I argued about this
    being "broken" for a while but then gave up, I understand why doing
    this differently does complicate the code, but at the same time improves
    performance)
    >
    > Yes, but adaptec guy says that go find one if you could because 5400 is good.
    > They told that 2xxxS has lower performance than 5400.
    >
    This would require faith in the fact that the aac driver will get fixed. It should
    be noted that I have not tested it with 5400 but tests with 2120S have random
    failures (shutdowns never complete, containerconfig gets read only sporadically,
    some operations hang for a relatively long time, etc.) so although I would like
    to use something like the above mentioned cards, it would jump in a dark, even
    compared with usually downplayed ATA RAID based solutions.

    > > And currently there are also the reliability issues with drivers like aac
    > > (Adaptec 2120S and 2200S, etc.) "no frills" SCSI or ATA controllers
    > > run much more reliably and have more user base so the issues get ironed
    > > out quicker.
    >
    > They are fixing the driver now, hopefully we will get newer one next week.
    >
    Scottl fixed a bug related to the aaccli interface about two weeks ago, havenīt
    heard from him since. Itīs good news that the driver is getting actively worked
    on. (although I keep hearing that his is not exactly getting paid on fixing it)

    Pete

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