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From Jan Hlavatý <hla...@code.cz>
Subject Re: alligned Vs Non Alligned log writes ..
Date Sat, 11 Dec 2004 17:56:55 GMT
Suresh Thalamati wrote:
> Thanks Jan. The numbers you got seems to show real performance gain with
> aligned writes.
> Test run by Dan & Sunitha & myself does not seem to show similar gain. I
> wonder if  this
> is anything to do with your disk being RAID ?
> 
> --what JVM are you running the test on  ?
> --is Write cache enabled/disabled  for the disk ?
> --what is the cache size on the disk ?

I had write cache on on the IDE disks. I turned it off
using hdparm -W0.
I got following numbers now:
java -cp . allignWritePerfTest2 kuk.bin 128

512 |  99.984375  |  103.078125  |  3.09423347398031%
256 |  53.5546875  |  53.1171875  |  -0.8169219547775413%
128 |  20.2421875  |  31.328125  |  54.76649942107295%
64 |  10.0  |  18.359375  |  83.59375%
32 |  9.265625  |  9.4296875  |  1.7706576728499215%
16 |  8.859375  |  9.0  |  1.5873015873015817%
12 |  8.8125  |  8.8984375  |  0.9751773049645323%
10 |  8.75  |  8.828125  |  0.8928571428571388%
8 |  8.578125  |  8.7265625  |  1.7304189435336923%
6 |  8.5546875  |  8.7109375  |  1.8264840182648356%
4 |  8.4375  |  8.8359375  |  4.7222222222222285%
2 |  8.390625  |  8.8359375  |  5.307262569832403%
1 |  8.4140625  |  9.1015625  |  8.170844939647168%

It is a lot slower than before generally (about 3 times).

There still seems to be performance gain in the case of 64k and 128k though. On other sizes,
there seems to be no significant gain now.

JVM: Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode, sharing).
I have 2 IDE drives like this (hdparm -I):
/dev/hde:

ATA device, with non-removable media
        Model Number:       WDC WD800JB-00CRA1
        Serial Number:      WD-WMA8E2112592
        Firmware Revision:  17.07W17
Standards:
        Supported: 5 4 3 2
        Likely used: 6
Configuration:
        Logical         max     current
        cylinders       16383   16383
        heads           16      16
        sectors/track   63      63
        --
        CHS current addressable sectors:   16514064
        LBA    user addressable sectors:  156301488
        device size with M = 1024*1024:       76319 MBytes
        device size with M = 1000*1000:       80026 MBytes (80 GB)
Capabilities:
        LBA, IORDY(can be disabled)
        bytes avail on r/w long: 40     Queue depth: 1
        Standby timer values: spec'd by Standard, with device specific minimum
        R/W multiple sector transfer: Max = 16  Current = 16
        Recommended acoustic management value: 128, current value: 254
        DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
             Cycle time: min=120ns recommended=120ns
        PIO: pio0 pio1 pio2 pio3 pio4
             Cycle time: no flow control=120ns  IORDY flow control=120ns
Commands/features:
        Enabled Supported:
           *    READ BUFFER cmd
           *    WRITE BUFFER cmd
           *    Host Protected Area feature set
           *    Look-ahead
                Write cache
           *    Power Management feature set
                Security Mode feature set
           *    SMART feature set
           *    Device Configuration Overlay feature set
                Automatic Acoustic Management feature set
                SET MAX security extension
           *    DOWNLOAD MICROCODE cmd
           *    SMART self-test
           *    SMART error logging
Security:
                supported
        not     enabled
        not     locked
        not     frozen
        not     expired: security count
        not     supported: enhanced erase
HW reset results:
        CBLID- above Vih
        Device num = 0 determined by CSEL
Checksum: correct


There is a ext3 filesystem on top of LVM2 logical volume on top of software raid 1 partition.

Jan

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