Subject: RAID over satalink SATA disks: poor performances
To: None <firstname.lastname@example.org>
From: Sebastien Erard <email@example.com>
Date: 12/29/2003 21:06:54
I have a SATALink 3112 controller with two 120GB SATA hard drives.
(see below the dmesg output for these devices)
If I access only one of them, I get up to 22MB/s trasfert rate on
the first GB (ussing dd bs=256k count=4096). Using dd one both
drives at the same time does not change much.
With a single partition one both of them, using bonnie++ (from
pkgsrc-current) shows some tranfert rates up to 50MB/s with a 1GB
file! (I checked this value with 'systat vm', it's impressive!)
But with bonnie++ on both drives at the same time, I nearly got
only 1MB/s (still systat vm).
My first idea was to use these two disks in RAID-0 (stripping).
But I noticed this strange behaviour: poor performance when
accessing both disks at the same time. Unusable with raidframe.
Is this a known limitation of the SiI3112?
Thanks for any answer,
PS: It seems that dd is doing some very small transfers, even
when specifying bs=256k, something like 11k tps. With
bonnie++, I only see 700 to 800 tps. All of this observed
witt systat vm.
[dmesg for satalink0, wd0 and wd1]
satalink0 at pci3 dev 12 function 0
satalink0: Silicon Image SATALink 3112 (rev. 0x01)
satalink0: SATALink BA5 register space disabled
satalink0: bus-master DMA support present
satalink0: primary channel wired to native-PCI mode
satalink0: using ioapic0 pin 20 (irq 3) for native-PCI interrupt
atabus2 at satalink0 channel 0
satalink0: secondary channel wired to native-PCI mode
atabus3 at satalink0 channel 1
satalink0: port 0: device present, speed: 1.5Gb/s
satalink0: port 1: device present, speed: 1.5Gb/s
wd0 at atabus2 drive 0: <Maxtor 6Y120M0>
wd0: drive supports 16-sector PIO transfers, LBA addressing
wd0: 114 GB, 238216 cyl, 16 head, 63 sec, 512 bytes/sect x 240121728 sectors
wd0: 32-bit data port
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd0(satalink0:0:0): using PIO mode 4, Ultra-DMA mode 6 (Ultra/133) (using
DMA data transfers)
wd1 at atabus3 drive 0: <Maxtor 6Y120M0>
wd1: drive supports 16-sector PIO transfers, LBA addressing
wd1: 114 GB, 238216 cyl, 16 head, 63 sec, 512 bytes/sect x 240121728 sectors
wd1: 32-bit data port
wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd1(satalink0:1:0): using PIO mode 4, Ultra-DMA mode 6 (Ultra/133) (using
DMA data transfers)
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