Tomasz Chmielewski wrote:
Mark Lord schrieb:
Tomasz Chmielewski wrote:
I have a ProLiant BL30p G1 machine running Debian Lenny (2.6.26 kernel).
It also has two identical, 2.5 inch WDC WD2500BEVE-00WZT0 IDE drives
(new drives, no smart/badblock errors). Both drives are connected to
a single IDE channel this machine has.
"hdparm -t" gives me different results for these drives: ~10 MB/s for
hda, and ~20 MB/s for hdb with "serverworks" driver on Debian's
2.6.26 kernel.
When using "pata-serverworks" with 2.6.28.7 kernel, hdparm shows the
same results (~10 MB/s for sda, ~20 MB/s for sdb).
However, when I run "dd if=/dev/sda of=/dev/null bs=64k", I can see
with iostat that for the first 7-8 seconds, reads are with ~10 MB/s
speed. Then, reads from sda are with ~20 MB/s or more and are on par
with sdb.
Similar dd test for sdb shows that it delivers with speed of ~20 MB/s
from the first second.
Is there an explanation for that?
..
Well, as you have shown, both hdparm and dd give the same results
when doing (almost) the same test: the first 3 seconds are slow.
But only for hda/sda. Not for hdb/sdb.
After that, I would assume that the kernel read-ahead algorithms
kick in better and improve things.
But 10-20Mbytes/sec is slow for most modern drives,
even for 2.5" drives. Older ones, sure, that's fine,
but the newest 2.5" drives should score between 40
and 100Mbytes/sec.
BTW, I didn't mention it - these machine have CSB5 IDE controllers.
drivers/ata/pata_serverworks.c say there are two revisions of these
controllers: one capable of UDMA 4, one capable of UDMA 5. I'm not sure
what revision it is:
00:0f.1 IDE interface: Broadcom CSB5 IDE Controller (rev 93) (prog-if 8a
[Master SecP PriP]) Subsystem: Broadcom CSB5 IDE Controller Control:
I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+ Stepping-
SERR+ FastB2B- DisINTx- Status: Cap- 66MHz- UDF- FastB2B- ParErr-
DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- Latency: 64
Region 0: I/O ports at 01f0 [size=8] Region 1: I/O ports at 03f4
[size=1] Region 2: I/O ports at 0170 [size=8] Region 3: I/O ports at
0374 [size=1] Region 4: I/O ports at 2000 [size=16] Kernel driver in
use: Serverworks_IDE Kernel modules: serverworks
Either way, yes, it should be faster.
(...)
The difference could easily be in the chipset used to communicate
with the drive.
Controller's chipset? That it has some extra doubts before it decides to
read
"faster" from the first drive (master), but doesn't have these doubts
when reading from the slave drive?
You said "serverworks" driver, and "pata-serverworks".
The kernel start up logs will have more information,
including the timing info chosen by libata.
Here is what 2.6.28.7 says:
[ 1.799408] ata1.00: ATA-8: WDC WD2500BEVE-00WZT0, 01.01A01, max
UDMA/100
[ 1.799413] ata1.00: 488397168 sectors, multi 8: LBA48.
[ 2.100115] ata1.01: ATA-8: WDC WD2500BEVE-00WZT0, 01.01A01, max
UDMA/100
[ 2.100118] ata1.01: 488397168 sectors, multi 8: LBA48.
[ 2.109007] ata1.00: configured for UDMA/100
[ 2.124554] ata1.01: configured for UDMA/100
[ 2.291564] scsi 0:0:0:0: Direct-Access ATA WDC WD2500BEVE-0
01.0 PQ: 0 ANSI: 5
[ 2.291761] scsi 0:0:1:0: Direct-Access ATA WDC WD2500BEVE-0
01.0 PQ: 0 ANSI: 5
[ 2.303851] Uniform Multi-Platform E-IDE driver
[ 2.318650] Driver 'sd' needs updating - please use bus_type methods
[ 2.318771] sd 0:0:0:0: [sda] 488397168 512-byte hardware sectors:
(250 GB/232 GiB)
[ 2.318790] sd 0:0:0:0: [sda] Write Protect is off
[ 2.318793] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 2.318822] sd 0:0:0:0: [sda] Write cache: disabled, read cache:
enabled, doesn't support DPO or FUA
[ 2.318901] sd 0:0:0:0: [sda] 488397168 512-byte hardware sectors:
(250 GB/232 GiB)
[ 2.318919] sd 0:0:0:0: [sda] Write Protect is off
[ 2.318922] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 2.318951] sd 0:0:0:0: [sda] Write cache: disabled, read cache:
enabled, doesn't support DPO or FUA
[ 2.318955] sda: sda1 sda2 sda3
[ 2.401158] sd 0:0:0:0: [sda] Attached SCSI disk
[ 2.401225] sd 0:0:1:0: [sdb] 488397168 512-byte hardware sectors:
(250 GB/232 GiB)
[ 2.401243] sd 0:0:1:0: [sdb] Write Protect is off
[ 2.401246] sd 0:0:1:0: [sdb] Mode Sense: 00 3a 00 00
[ 2.401274] sd 0:0:1:0: [sdb] Write cache: disabled, read cache:
enabled, doesn't support DPO or FUA
[ 2.401332] sd 0:0:1:0: [sdb] 488397168 512-byte hardware sectors:
(250 GB/232 GiB)
[ 2.401350] sd 0:0:1:0: [sdb] Write Protect is off
[ 2.401353] sd 0:0:1:0: [sdb] Mode Sense: 00 3a 00 00
[ 2.401382] sd 0:0:1:0: [sdb] Write cache: disabled, read cache:
enabled, doesn't support DPO or FUA
[ 2.401385] sdb: sdb1 sdb2
[ 2.453608] sd 0:0:1:0: [sdb] Attached SCSI disk
..
Everything looks configured correctly, so the only explanations
for the slow (10/20MB/sec) speeds are the CPU/RAM, or other system activity.
As for the disparity in initial throughput between the master/slave drives,
you could try reversing the two drives (swap them on the cable if using
"cable select", otherwise rejumper the master/slave setup). Then see if the
slow start follows the specific drive to its new position on the cable,
or if the master ("a") drive is always slower.
Cheers
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