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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