[7449] in linux-scsi channel archive
RE: Please Help - SCSI RAID device very slow
daemon@ATHENA.MIT.EDU (Matthew Clark)
Wed Oct 27 17:14:05 1999
Reply-To: <m.r.clark@btinternet.com>
From: "Matthew Clark" <m.r.clark@btinternet.com>
To: "linux-scsi" <linux-scsi@vger.rutgers.edu>,
"linux-raid" <linux-raid@vger.rutgers.edu>,
"Scott Marlowe" <smarlowe@ihs.com>
Date: Wed, 27 Oct 1999 22:05:52 +0100
Message-ID: <005c01bf20bf$0d916ce0$0100a8c0@netdespatch.co.uk>
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In-Reply-To: <Pine.LNX.4.04.9910271417050.7263-100000@css120.ihs.com>
Thanks for replying...
> The AMI MegaRAIDs I've worked with (the 428) had an Intel i960 RISC
> processor integrated onto the megaraid card, along with several
> SymBIOS 8xx
> series SCSI controller chips. The i960 generates parity data and controls
> the RAID arrays, while the Symbios chips interface to the HDs
> under control
> of the i960.
This is what someone else has mentioned .. so the i960 is actually
controlling the onboard Symbios controllers...
>
> The newer MegaRAID cards can now "hijack" your other Symbios based
> controllers and make them part of the "collective" that is the megaraid.
>
Yikes - That sounds unplesant! Fortunately my other controller is an adaptec
U2W (aic7xxx)
> How slow is too slow? What numbers do you get from hdparm -tT?
Well .. hdparm -tT isn't "so" bad - here's the output....
#hdparm -tT /dev/sda
/dev/sda:
Timing buffer-cache reads: 64 MB in 0.61 seconds =104.92 MB/sec
Timing buffered disk reads: 32 MB in 1.50 seconds =21.33 MB/sec
(are 32 & 64 meg enough for these tests??)
it's writing that's the BIG problem - check out this output from bonnie..
-------Sequential Output-------- ---Sequential
Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per
Char- --Block--- --Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec
%CPU
1* 300 446 7.0 447 1.7 2440 4.9 4926 61.4 26823 24.6 1047.2
14.1
:-(
> No, the MegaRAID is what it should be talking to. The Symbios controllers
> are now subsystems to the MegaRAID.
Right - well I'm glad you said that.. that was confusing the hell out of me!
Both you and Gerard Roudier have confirmed that now..
I never heard of the i960 controlling controllers like that.. mind you I
never claimed to be a hardware guru :-)
Regards,
Matthew Clark.
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