sa and mpt in FreeBSD 11.0-RELEASE-p2

[Dirk-Willem van Gulik]

A machine, recently upgraded from 8.4 to FreeBSD 11.0-RELEASE-p2 seems to have lost pretty much any and all performance on mpt(4) with its attached tape drives

Read performance is around 50Mbyte/second - and write a paltry 100-200kbyte/second (and occasionally hitting 800kbyte/second) (from/to memory disk&/dev/null; no risk of shoe shining, compression off).

SCSI bus looks happy; with no kernel messages. Output of the DLT script below.

Normal LTO drives in a tape robot, G9 server; pretty much all SAS *except* for a U320 to tape drive with the performance issue. Active terminator.

Does this ring a bell with anyone? Was anything changed in either the sa or mpt driver since 8.x ? 

One odd thing is that a 'dd(1)' -without- a block size (compression is off, data is a prepared urandom file on md disk) writes much faster -- while on 8.x one -had- to use a sane blockwise to get the 'normal' speed of around 120Mbyte/second. Could it be that one needs to fiddle with MAXPHYS (which AFAIK is a readonly sysctl).

Dw.

DLT /  http://www.freebsddiary.org/tape-testing.php
READING
                Corrected errors with substantial delay: 0
                Corrected errors with possible delay   : 0
                Total errors                           : 0
                Total errors corrected                 : 0
                Total times correction algorithm used  : 0
                Total bytes processed                  : 8590352388
                Total corrected errors / GB            : 0
                Total uncorrected errors               : 0
                Read compression ratio                 : 101%
                On tape Mbytes read                    : 2
                On tape kbytes read residual           : 329320
WRITING
                Corrected errors with substantial delay: 154
                Corrected errors with possible delay   : 0
                Total errors                           : 0
                Total errors corrected                 : 0
                Total times correction algorithm used  : 168
                Total bytes processed                  : 4909148037124
                Total corrected errors / GB            : 0
                Total uncorrected errors               : 0
                Write compression ratio                : 99%
                Host requested Mbytes written          : 1442
                Host requested kbytes written residual : 115996
                On tape Mbytes written                 : 1443
                On tape kbytes written residual        : 0

camcontrol devlist

<QUANTUM ULTRIUM 4 W52T>           at scbus3 target 5 lun 0 (sa0,pass0)
<QUANTUM UHDL 0091>                at scbus3 target 5 lun 1 (ch0,pass1)
<HP RAID 0 OK>                     at scbus4 target 0 lun 0 (pass2,da0)
<HP RAID 1(1+0) OK>                at scbus6 target 0 lun 0 (pass3,da1)
<HP RAID 0 OK>                     at scbus6 target 1 lun 0 (pass4,da2)
<QUANTUM ULTRIUM 4 W52T>           at scbus7 target 5 lun 0 (sa1,pass5)
<QUANTUM UHDL 0091>                at scbus7 target 5 lun 1 (ch1,pass6)

mt rblim
/dev/nsa0:
    min blocksize 1 byte
    max blocksize 16777215 bytes
    granularity 1 byte

mt status, ostatus and errstatus

Mode      Density              Blocksize      bpi      Compression
Current:  0x46:LTO-4           variable       323215   disabled
---------available modes---------
0:        0x46:LTO-4           variable       323215   0x1
1:        0x46:LTO-4           variable       323215   0x1
2:        0x46:LTO-4           variable       323215   0x1
3:        0x46:LTO-4           variable       323215   0x1
---------------------------------
Current Driver State: at rest.
---------------------------------
File Number: 0  Record Number: 0        Residual Count 0


Drive: sa0: <QUANTUM ULTRIUM 4 W52T> Serial Number: HU1027B53Y
---------------------------------
Mode      Density              Blocksize      bpi      Compression
Current:  0x46:LTO-4           variable       323215   disabled
---------------------------------
Current Driver State: at rest.
---------------------------------
Partition:   0      Calc File Number:   0     Calc Record Number: 0
Residual:    0  Reported File Number:   0 Reported Record Number: 0
Flags: BOP

Last I/O Residual: 0
 Last I/O Command: 0A 00 02 00 00 00 00 00 00 00 00 00 00 00 00 00
   Last I/O Sense:

         70 00 0B 00 00 00 00 10 00 00 00 00 47 03 00 00
         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Last Control Residual: 0
 Last Control Command: 34 06 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   Last Control Sense:

         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00