From owner-freebsd-current  Sat Feb 20 18:13:19 1999
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From: Dennis Glatting <dennis.glatting@software-munitions.com>
Date: Sat, 20 Feb 99 18:12:14 -0800
To: "Kenneth D. Merry" <ken@plutotech.com>
Subject: Re: Slow seq. write on Seagate ST36530N
Cc: freebsd-current@FreeBSD.ORG
Reply-To: dennis.glatting@plaintalk.bellevue.wa.us
References: <199902210029.RAA15447@panzer.plutotech.com>
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> > Just to throw my voice in, I get crappy SCSI performance on my
> > three SCSI card Dell. I don't understand why.
>
> Umm, you're going to have to be a little more specific than that.
>
> You do have one of those slow Western Digital drives, which
> could cause some problems.
>

The WD drive is on its own controller. The ST410800W is on its own
controller. The two ST43400Ns are together on the third
controller.

On the ST410800W I am getting, according to iozone:

> btw# iozone 1024 8192 /ExternalDisk/junk
> 	....
> Writing the 1024 Megabyte file, '/ExternalDisk/junk'...299.609375 seconds
> Reading the file...178.609375 seconds
>
> IOZONE performance measurements:
>         3583805 bytes/second for writing the file
>         6011676 bytes/second for reading the file
>

Since this is a 16 bit device with 10 MHz transfer rate I expect
better, or should I not? According to the disk specs the average
internal transfer rate is 7.2 MB/sec, 20 MB/sec external
burst.

The following is an examination of the device's mode pages. I'm
currently looking at each variable and their meaning, though I
am not a SCSI guru.


> ==> 0
>
> 00 00 00 00 00 00 00 00
> 00 00 00 00 00 00 00
>
>
>
>
> ==> 1
>
> AWRE (Auto Write Reallocation Enbld):  1
> ARRE (Auto Read Reallocation Enbld):  0
> TB (Transfer Block):  0
> RC (Read Continuous):  0
> EER (Enable Early Recovery):  1
> PER (Post Error):  0
> DTE (Disable Transfer on Error):  0
> DCR (Disable Correction):  0
> Read Retry Count:  27
> Correction Span:  48
> Head Offset Count:  0
> Data Strobe Offset Count:  0
> Write Retry Count:  1
> Recovery Time Limit:  65535
>
>
>
>
> ==> 2
>
> Buffer Full Ratio:  44
> Buffer Empty Ratio:  238
> Bus Inactivity Limit:  10
> Disconnect Time Limit:  0
> Connect Time Limit:  0
> Maximum Burst Size:  0
> DTDC:  0
>
>
>
>
> ==> 3
>
> Tracks per Zone:  27
> Alternate Sectors per Zone:  9
> Alternate Tracks per Zone:  0
> Alternate Tracks per Logical Unit:  27
> Sectors per Track:  133
> Data Bytes per Physical Sector:  512
> Interleave:  1
> Track Skew Factor:  10
> Cylinder Skew Factor:  21
> SSEC:  0
> HSEC:  1
> RMB:  0
> SURF:  0
>
>
>
>
> ==> 4
>
> Number of Cylinders:  4926
> Number of Heads:  27
> Starting Cylinder-Write Precompensation:  0
> Starting Cylinder-Reduced Write Current:  0
> Drive Step Rate:  0
> Landing Zone Cylinder:  0
> RPL:  0
> Rotational Offset:  0
> Medium Rotation Rate:  5400
>
>
>
>
> ==> 7
>
> EER:  0
> PER:  1
> DTE:  0
> DCR:  0
> Verify Retry Count:  27
> Verify Correction Span:  48
> Verify Recovery Time Limit:  65535
>
>
>
>
> ==> 8
>
> IC:  0
> ABPF:  0
> CAP:  1
> DISC:  1
> SIZE:  0
> WCE:  1
> MF:  0
> RCD:  0
> Demand Retention Priority:  0
> Write Retention Priority:  0
> Disable Pre-fetch Transfer Length:  65535
> Minimum Pre-fetch:  0
> Maximum Pre-fetch:  29
> Maximum Pre-fetch Ceiling:  477
>
>
>
>
> ==> 10
>
> RLEC:  0
> Queue Algorithm Modifier:  1
> QErr:  0
> DQue:  0
> EECA:  0
> RAENP:  0
> UAAENP:  0
> EAENP:  0
> Ready AEN Holdoff Period:  0
>
>
>
>
> ==> 12
>
> 80 00 00 16 00 00 00 00
> 00 00 00 13 3d 1a 00 00
> 00 00 00 00 10 00 00 00
> 00 00 00 00 00 00 00 00
> 00 00 00
>
>


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