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Date:      Fri, 15 Feb 2013 10:58:52 -0500
From:      Douglas Gilbert <dgilbert@interlog.com>
To:        jackson wang <jackson4015@gmail.com>
Cc:        freebsd-scsi@freebsd.org
Subject:   Re: Link rate problem of SAS HDD
Message-ID:  <511E5B3C.8040400@interlog.com>
In-Reply-To: <CAHPbiTZOYhzUQFMJnxVQY6woy27JACDcYgnofCZpmr8xw8yZjg@mail.gmail.com>
References:  <CAHPbiTZOYhzUQFMJnxVQY6woy27JACDcYgnofCZpmr8xw8yZjg@mail.gmail.com>

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On 13-02-15 04:02 AM, jackson wang wrote:
> Hello,All.
>
> I have a SAS HDD,have some demands as following:
>
> 1.Use SCSI command to get the supported link rates,ex:1.5? 3.0? or 6.0 Gb/s;
> 2.Get current working link rate with SCSI CMD;
> 3.Need to downgrade 6.0gb/s to 3.0gb/s with SCSI CMD because some RAID
> card had bugs,
> so speed negotiation sometimes failed;
>
> I know many RAID cards have management tool:CLI,which could make it,
> but not all system install that
> tool, so using SCSI command is the only option.

May I immodestly propose sdparm which is written for
Linux but ported to FreeBSD (Solaris and Windoze). You
will need to familiarize yourself with SAS "phy control
and discover" mode page. Then see:
     http://sg.danny.cz/sg/sdparm.html

There is an example in the Examples section. The items of
interest are: Programmed minimum link rate and Programmed
maximum link rate. By changing them and resetting the disk
you constrain the following speed negotiation.

You may also be interested in my sg3_utils (for general SCSI
commands) and smp_utils (for SAS expanders) packages. They
are also ported to FreeBSD.

Doug Gilbert






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