Re: RAID-3? (was: cvs commit: src MAINTAINERS)

From: Pawel Jakub Dawidek (pjd_at_FreeBSD.org)
Date: 08/20/04

  • Next message: Petri Helenius: "Re: RAID-3?" 
    Date: Fri, 20 Aug 2004 21:35:47 +0200
To: Greg 'groggy' Lehey <grog@FreeBSD.org>

    On Thu, Aug 19, 2004 at 12:13:59PM +0930, Greg 'groggy' Lehey wrote:
    +> On Tuesday, 17 August 2004 at 15:16:12 +0200, Pawel Jakub Dawidek wrote:
    +> > On Tue, Aug 17, 2004 at 10:10:20PM +0930, Greg 'groggy' Lehey wrote:
    +> > +> On the contrary. RAID-3 requires byte-level striping, which is
    +> > +> ridiculous on the hardware that FreeBSD supports.
    [...]
    +> > Want to compare performance with vinum's RAID5?:)
    +>
    +> Feel free. But do it with more than a single process accessing the
    +> disks.

    Tests were done using this HW:

    CPU: Pentium II/Pentium II Xeon/Celeron (534.55-MHz 686-class CPU)
      Origin = "GenuineIntel" Id = 0x665 Stepping = 5
      Features=0x183fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR>
    real memory = 67108864 (64 MB)
    avail memory = 60256256 (57 MB)
    MPTable: <OEM00000 PROD00000000>
    FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
    [...]
    iir0: <ICP Disk Array Controller> mem 0xd8100000-0xd8103fff irq 17 at device 13.0 on pci0
    [...]
    da0 at iir0 bus 2 target 0 lun 0
    da0: <ICP Host Drive #00 > Fixed Direct Access SCSI-2 device
    da0: Tagged Queueing Enabled
    da0: 8675MB (17767890 512 byte sectors: 255H 63S/T 1106C)
    da1 at iir0 bus 2 target 1 lun 0
    da1: <ICP Host Drive #01 > Fixed Direct Access SCSI-2 device
    da1: Tagged Queueing Enabled
    da1: 8675MB (17767890 512 byte sectors: 255H 63S/T 1106C)
    da2 at iir0 bus 2 target 2 lun 0
    da2: <ICP Host Drive #02 > Fixed Direct Access SCSI-2 device
    da2: Tagged Queueing Enabled
    da2: 8675MB (17767890 512 byte sectors: 255H 63S/T 1106C)

    The software you can find under /usr/src/tools/tools/raidtest/ in HEAD
    branch.
    Test has been done for 10000 random requests (offset, size and operation
    type was random).

    RAID3:
                    Number of Bytes per Requests per
    Operations processes second second
    ----------------------------------------------------------------------
    READ 3 6329500 95
    READ 15 8981047 135
    READ 100 10719314 161
    WRITE 3 5073263 76
    WRITE 15 7467387 112
    WRITE 100 8631136 129
    READ/WRITE 3 6041795 90
    READ/WRITE 15 8104847 121
    READ/WRITE 100 9494250 142

    RAID5:
                    Number of Bytes per Requests per
    Operations processes second second
    ----------------------------------------------------------------------
    READ 3 6041795 90
    READ 15 14768833 222
    READ 100 19546985 294
    WRITE 3 3479568 52
    WRITE 15 5403231 81
    WRITE 100 6211191 93
    READ/WRITE 3 4521071 68
    READ/WRITE 15 7911875 119
    READ/WRITE 100 9360528 140

    As you can see RAID5 is only faster in READ tests for 15 and 100 processes
    working in parallel. As I can see, RAID3 is faster in all the rest tests.

    Of course you are welcome to try by yourself.

    Anyway, if I can ask for something. Think twice before calling something
    ridiculous without understanding.

    PS. I wonder about read optimization, so parity component can be also
        used for reading in round-robin fashion... 

    -- 
Pawel Jakub Dawidek                       http://www.FreeBSD.org
pjd@FreeBSD.org                           http://garage.freebsd.pl
FreeBSD committer                         Am I Evil? Yes, I Am!

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