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Title: HD-CXU2 slow on linux
Post by: drewp on October 30, 2009, 03:13:40 AM

Raw access to the disk is running around 3-6MB/sec. I'm pretty sure it worked faster before; my notes show some 16MB/sec and 22MB/sec operations on a mirror between this disk and another one. I've been running the disk for about a month.

Here's the current behavior:

# uname -a

Linux slash 2.6.30-02063009-generic #02063009 SMP Thu Oct 8 13:29:05 UTC 2009 x86_64 GNU/Linux

# grep DESC /etc/lsb-release

DISTRIB_DESCRIPTION="Ubuntu 9.04"

# dmesg

...

[ 7.900188] usb-storage: device scan complete

[ 7.901777] scsi 6:0:0:0: Direct-Access WD 10EADS External 1.75 PQ: 0 ANSI: 4

[ 7.902100] sd 6:0:0:0: Attached scsi generic sg2 type 0

[ 7.903269] sd 6:0:0:0: [sdc] 1953525168 512-byte hardware sectors: (1.00 TB/931 GiB)

[ 7.904664] sd 6:0:0:0: [sdc] Write Protect is off

[ 7.904670] sd 6:0:0:0: [sdc] Mode Sense: 23 00 00 00

[ 7.904673] sd 6:0:0:0: [sdc] Assuming drive cache: write through

[ 7.906657] sd 6:0:0:0: [sdc] Assuming drive cache: write through

[ 7.906710] sdc: sdc1

[ 7.935389] sd 6:0:0:0: [sdc] Attached SCSI disk

[ 8.156175] usb-storage: device scan complete

[ 8.157822] scsi 7:0:0:0: Direct-Access BUFFALO HD-CXU2 0.28 PQ: 0 ANSI: 4

[ 8.158138] scsi 7:0:0:1: CD-ROM BUFFALO Virtual Cdrom 0.28 PQ: 0 ANSI: 0

[ 8.158430] sd 7:0:0:0: Attached scsi generic sg3 type 0

[ 8.159666] sr0: scsi3-mmc drive: 0x/0x xa/form2 tray

[ 8.159672] Uniform CD-ROM driver Revision: 3.20

[ 8.159773] sr 7:0:0:1: Attached scsi CD-ROM sr0

[ 8.159831] sr 7:0:0:1: Attached scsi generic sg4 type 5

[ 8.160141] sd 7:0:0:0: [sdd] 1952255280 512-byte hardware sectors: (999 GB/930 GiB)

[ 8.161664] sd 7:0:0:0: [sdd] Write Protect is off

[ 8.161670] sd 7:0:0:0: [sdd] Mode Sense: 00 26 00 00

[ 8.161672] sd 7:0:0:0: [sdd] Assuming drive cache: write through

[ 8.163665] sd 7:0:0:0: [sdd] Assuming drive cache: write through

[ 8.163717] sdd: sdd1

[ 15.167065] sd 7:0:0:0: [sdd] Attached SCSI disk

# cat scsi/usb-storage/9

Host scsi9: usb-storage

Vendor: BUFFALO

Product: USB-SATA Bridge

Serial Number: 00101007000B0EAC0

Protocol: Transparent SCSI

Transport: Bulk

Quirks: SANE_SENSE

# head /sys/block/sdd/device/{max_sectors,rev,scsi_level}

==> /sys/block/sdd/device/max_sectors <==

240

==> /sys/block/sdd/device/rev <==

0.28

==> /sys/block/sdd/device/scsi_level <==

(the other numbers looked boring)

// this other usb disk works as expected

# hdparm -t /dev/sdc

/dev/sdc:

Timing buffered disk reads: 78 MB in 3.04 seconds = 25.65 MB/sec

// the buffalo one is running very slow

# hdparm -t /dev/sdd

/dev/sdd:

Timing buffered disk reads: 14 MB in 3.04 seconds = 4.61 MB/sec

// a few more repetitions:

Timing buffered disk reads: 26 MB in 3.35 seconds = 7.77 MB/sec

Timing buffered disk reads: 2 MB in 3.98 seconds = 514.12 kB/sec

Timing buffered disk reads: 12 MB in 3.18 seconds = 3.77 MB/sec

Timing buffered disk reads: 22 MB in 3.41 seconds = 6.45 MB/sec

Timing buffered disk reads: 18 MB in 3.04 seconds = 5.92 MB/sec

The behavior is the same if I unplug the sdc disk. I looked around for other processes that might be talking to sdd at the same time, but I can't find any. And, the contents of /sys/block/sdd/device/iorequest_cnt doesn't change unless I run hdparm, which makes me think nothing else on the OS is accessing the disk at the same time.

This is unusual behavior, right? Are there more diagnostics I can run or settings I can change?

Title: Re: HD-CXU2 slow on linux
Post by: JoshC on October 30, 2009, 05:37:17 AM

There is nothing you can change. Also we dont support the device using Linux.

Buffalo Forums

Products => Storage => Topic started by: drewp on October 30, 2009, 03:13:40 AM