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I got a new machine with GA-p55A-ud3 mobo and a WDC WD10EARS 1T disk. When I tried to benchmark the disk IO, I was suprised by the low write speed:
[Children see throughput for 1 initial writers = 35962.63 KB/sec
Parent sees throughput for 1 initial writers = 35962.63 KB/sec
Min throughput per process = 35962.63 KB/sec
Max throughput per process = 35962.63 KB/sec
Avg throughput per process = 35962.63 KB/sec
Min xfer = 2048000.00 KB
Children see throughput for 1 rewriters = 42461.44 KB/sec
Parent sees throughput for 1 rewriters = 42461.44 KB/sec
Min throughput per process = 42461.44 KB/sec
Max throughput per process = 42461.44 KB/sec
Avg throughput per process = 42461.44 KB/sec
Min xfer = 2048000.00 KB
]
Just 35 ~ 42 MB/s. I installed debian lenny 2.6.26 and I suspected maybe this is because I am using old kernel. So I compiled a 2.6.32.21 and reboot.
However, the result is still the same.
Why is this?
The related output from my lspci:
00:1f.2 SATA controller: Intel Corporation Ibex Peak 6 port SATA AHCI Controller (rev 06)
The related output from my dmesg:
[ 2.182356] ahci 0000:00:1f.2: version 3.0
[ 2.182365] ahci 0000:00:1f.2: PCI->APIC IRQ transform: INT B -> IRQ 19
[ 2.188038] ahci 0000:00:1f.2: irq 28 for MSI/MSI-X
[ 2.188060] ahci: SSS flag set, parallel bus scan disabled
[ 2.209290] ahci 0000:00:1f.2: AHCI 0001.0300 32 slots 6 ports 3 Gbps 0x3f impl SATA mode
[ 2.221870] ahci 0000:00:1f.2: flags: 64bit ncq sntf stag pm led clo pmp pio slum part ems apst
[ 2.235972] ahci 0000:00:1f.2: setting latency timer to 64
[ 2.273292] scsi0 : ahci
[ 2.280626] scsi1 : ahci
[ 2.287984] scsi2 : ahci
[ 2.295374] scsi3 : ahci
[ 2.302491] scsi4 : ahci
[ 2.309338] scsi5 : ahci
[ 2.403150] ahci 0000:02:00.0: PCI->APIC IRQ transform: INT A -> IRQ 16
[ 2.411320] ahci 0000:02:00.0: irq 29 for MSI/MSI-X
[ 2.425344] ahci 0000:02:00.0: AHCI 0001.0200 32 slots 8 ports 6 Gbps 0xff impl SATA mode
[ 2.441704] ahci 0000:02:00.0: flags: 64bit ncq pio
[ 2.450182] ahci 0000:02:00.0: setting latency timer to 64
[ 2.450442] scsi6 : ahci
[ 2.458744] scsi7 : ahci
[ 2.466789] scsi8 : ahci
[ 2.474597] scsi9 : ahci
[ 2.482142] scsi10 : ahci
[ 2.489388] scsi11 : ahci
[ 2.496294] scsi12 : ahci
[ 2.502870] scsi13 : ahci
The related output from my lshw:
*-storage
description: SATA controller
product: Ibex Peak 6 port SATA AHCI Controller
vendor: Intel Corporation
physical id: 1f.2
bus info: pci@0000:00:1f.2
logical name: scsi0
version: 06
width: 32 bits
clock: 66MHz
capabilities: storage msi pm ahci_1.0 bus_master cap_list emulated
configuration: driver=ahci latency=0 module=ahci
*-disk:0
description: ATA Disk
product: WDC WD10EARS-00Y
vendor: Western Digital
physical id: 0
bus info: scsi@0:0.0.0
logical name: /dev/sda
version: 80.0
serial: WD-WCAV5D367278
size: 931GiB (1TB)
capabilities: partitioned partitioned:dos
configuration: ansiversion=5 signature=0008598f
...
I think problem is these Caviar Green "EARS" drives apparently use Advanced Format Technology (AF), i.e. the sector size on the drive is 4K instead of the standard 512 bytes:
From my limited googling, WD does not support AF on linux. Very poor performance is reported if the drive partition boundaries are not aligned with the 4K sectors. There are some workarounds to insure proper alignment using fdisk to create the partitions:
kilgoretrout, Thanks for reply.
I am using iozone.
And it's helpful when I set the first partition's starting sector to 64. The write rate climbs to 72MB/s!
But now I think I got another problem. I have 2 partitions on this disk. And the interesting thing is the write performance of the second partition is lower than the first one.
Here is result of fdisk -l - u :
Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x0003e835
Device Boot Start End Blocks Id System
/dev/sdd1 64 976751999 488375968 83 Linux
/dev/sdd2 976752000 2197708064 610478032+ 83 Linux
For /dev/sdd1, write speed is around 70MB/s. But for /dev/sdd2 only 60MB/s. I do tested a few times.
Any idea on this?
Some say that the drive has to be formatted under windows 7, so that alignment is done automatically. If you dont have windows 7, gparted 0.6.0+ can do the same thing on any filesystem.
That angular velocity speed thing has to be the most stupid excuse for poor performance.
At the above test, why don't the other drives from the other manifacturers have/suffer from the same physics "problem"?
That angular velocity speed thing has to be the most stupid excuse for poor performance.
If you have read the post I was answering two you would know that the angular velocity explanation was not meant to explain overall poor performance, but to explain why the harddrive is not transfering data at the same speed over the whole disk.
Should read carefully before calling something stupid.
If you had carefully read the article at xbit you also would know that the EARS drives work only internally with 4K units but act externally as drives with 512 byte units. Therefore it is essential that you align partitions to sectors that are dividable by 8. This is exactly done by th OP, his drives partitions are aligned.
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