Comment 24 for bug 216878

Hi Zhang,
  you're welcome.

It is actually possible to get very high performance from SATA disks,
comparable to those of SAS or SCSI, by using a technique called
short-stroking.

If you understand the mechanics of the disks, you can actually build a
system with very low latency. You can get this by placing the most accessed
files on the outer zone of your disk, thus getting the max rotational speed
and reducing head movement.

This way you can greatly reduce the arm movement and get higher throughputs!
:)

2009/2/16 ZhangInSeattle <email address hidden>

> Hi Stek79,
>
> Thanks for your reply!
>
> I understand the hdparm result is the best possible speed. But the
> difference between 42.84MB/sec and 5MB/sec still shocked me.
> It kinda implied that the file system (I'm using ext3) needs more
> optimization to store big files in the way the hard disk can sequentially
> read (with minimum arm movement). (I don't know much about ext3, maybe it
> did the optimization already).
>
> My laptop (thinkpad t61) is purchased in October 2008. It has a SATA
> disk. It should have a much better performance than 5MB/sec imho :-)
>
>
> Thanks!
> ZhangInSeattle
>
> --
> [regression]Slow disk transfer rate on Hardy
> https://bugs.launchpad.net/bugs/216878
> You received this bug notification because you are a direct subscriber
> of the bug.
>
> Status in "linux" source package in Ubuntu: Triaged
>
> Bug description:
> Hi,
> upgrading from Gutsy to Hardy I've seen a considerable HD transfer rate
> slowdown.
>
> I have a machine with two IDE disks, both are udma5 capable. In Gutsy, they
> were recognised as 'hd[ab]' and I with hdparm sequential thoughput was:
>
> /dev/hdb:
> Timing buffered disk reads: 172 MB in 3.01 seconds = 57.19 MB/sec
>
> which is quite correct for that kind of drive.
>
> In Hardy, they are recognized as 'sd[ab]', and the performance regarding
> transfer rate is LESS THAN HALF:
>
> /dev/sdb:
> Timing buffered disk reads: 78 MB in 3.01 seconds = 25.92 MB/sec
>
> That slowdown is visible also during file transfer operations, obviously.
> One thing I've noticed is that in the dmesg, my drive is set at UDMA/33, and
> also hdparm reports that udma2 is currently configured:
>
> sudo hdparm -i /dev/sdb
>
> /dev/sdb:
>
> Model=WDC WD2500JB-00GVC0 , FwRev=08.02D08, SerialNo=
> WD-WCAL78023606
> Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
> RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=74
> BuffType=DualPortCache, BuffSize=8192kB, MaxMultSect=16, MultSect=?16?
> CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=488397168
> IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
> PIO modes: pio0 pio1 pio2 pio3 pio4
> DMA modes: mdma0 mdma1 mdma2
> UDMA modes: udma0 udma1 *udma2 udma3 udma4 udma5
> AdvancedPM=no WriteCache=enabled
> Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6
>
> * signifies the current active mode
>
> I've seen a number of users complaining about that, a number of bugs with
> status Incomplete or Release Fixed. I can say that with the latest Hardy
> patches (as of now), the problem is still there. Will that be fixed before
> the final release? If not, that can be a huge performance penalty!
>
> Here are some infos. I'm willing to help to solve the problem, just ask if
> you need any info.
> ste@ste-ubuntu:~$ lsb_release -rd
> Description: Ubuntu hardy (development branch)
> Release: 8.04
>
> Pertinent dmesg output:
>
> [ 35.085132] libata version 3.00 loaded.
> [ 35.460830] pata_via 0000:00:11.1: version 0.3.3
> [ 35.463781] scsi0 : pata_via
> [ 35.465345] scsi1 : pata_via
> [ 35.465441] ata1: PATA max UDMA/100 cmd 0x1f0 ctl 0x3f6 bmdma 0xcc00 irq
> 14
> [ 35.465446] ata2: PATA max UDMA/100 cmd 0x170 ctl 0x376 bmdma 0xcc08 irq
> 15
> [ 35.637026] ata1.00: ATA-6: Maxtor 5T030H3, TAH71DP0, max UDMA/100
> [ 35.637034] ata1.00: 60030432 sectors, multi 16: LBA
> [ 35.638417] ata1.01: ATA-6: WDC WD2500JB-00GVC0, 08.02D08, max UDMA/100
> [ 35.638424] ata1.01: 488397168 sectors, multi 16: LBA48
> [ 35.638446] ata1.00: limited to UDMA/33 due to 40-wire cable
> [ 35.638450] ata1.01: limited to UDMA/33 due to 40-wire cable
> [ 35.652916] ata1.00: configured for UDMA/33
> [ 35.669962] ata1.01: configured for UDMA/33
> [ 36.136471] ata2.00: ATAPI: LG DVD-ROM DRD-8160B, 1.01, max
> UDMA/33
> [ 36.136502] ata2.01: ATAPI: HL-DT-ST GCE-8160B, 1.02, max MWDMA2
> [ 36.300210] ata2.00: configured for UDMA/33
> [ 36.464034] ata2.01: configured for MWDMA2
> [ 36.464239] scsi 0:0:0:0: Direct-Access ATA Maxtor 5T030H3
> TAH7 PQ: 0 ANSI: 5
> [ 36.464959] scsi 0:0:1:0: Direct-Access ATA WDC WD2500JB-00G
> 08.0 PQ: 0 ANSI: 5
>
> Kernel:
>
> Linux ste-ubuntu 2.6.24-16-generic #1 SMP Thu Apr 10 13:23:42 UTC 2008 i686
> GNU/Linux
>
> For other info, just let me know! BTW, congrats for the GREAT WORK!!!
>