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.:B:.

Forum Fellow

Registered: 2006-11-26

Posts: 5,819

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External USB disks dog slow

Okay... So I bought three 2,5" USB HDD enclosures the other day. Two of them have 500 GB Samsungs in them, the third a 250 GB Seagate one.

The external drives already gave problems from the get-go but I thought it was fine to disregard them - it seems the problems lie deeper, though. Since one of the Samsungs (haven't checked both but it is very probable the second suffers from the same problem) and the Seagate both exhibit similar behaviour I'd think it's the chipset of the USB enclosure that is causing the trouble (cheap-ass Icy Box enclosures yay).

Anyway, some data:

External USB HD on the laptop (Samsung one):

Bus 005 Device 020: ID 04fc:0c25 Sunplus Technology Co., Ltd

External USB HD on the server (Seagate one):

Bus 002 Device 003: ID 04fc:0c25 Sunplus Technology Co., Ltd

I have googled the PCI ID but not found anything peculiar.

Performance tests with hdparm give this (first one is the Samsung, second one the Seagate):

root@hermes stijn hdparm -Tt /dev/samsung1 

/dev/samsung1:
 Timing cached reads:   966 MB in  2.00 seconds = 482.68 MB/sec
 Timing buffered disk reads:   74 MB in  3.05 seconds =  24.25 MB/sec

[root@amalthea stijn]# hdparm -Tt /dev/sdd

/dev/sdd:
 Timing cached reads:   1070 MB in  2.00 seconds = 535.23 MB/sec
 Timing buffered disk reads:   56 MB in  3.03 seconds =  18.49 MB/sec

As you can see, for two modern S-ATA HDs, this is pretty shitty (I really hope the onboard logic of the USB enclosure isn't the culprit but I'm afraid it is). Dmesg output looks fine.

Furthermore, both HDs absolutely refuse to cooperate with hdparm when you query them for info:

root@hermes stijn hdparm -I /dev/samsung1 

/dev/samsung1:
 HDIO_DRIVE_CMD(identify) failed: Input/output error
root@hermes stijn hdparm -i /dev/samsung1 

/dev/samsung1:
 HDIO_GET_IDENTITY failed: Invalid argument

[root@amalthea stijn]# hdparm -I /dev/sdd

/dev/sdd:
 HDIO_DRIVE_CMD(identify) failed: Input/output error
[root@amalthea stijn]# hdparm -i /dev/sdd

/dev/sdd:
 HDIO_GET_IDENTITY failed: Invalid argument

Setting DMA on those drives obviously doesn't work either:

root@hermes stijn hdparm -d1 /dev/samsung1 

/dev/samsung1:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Invalid argument
 HDIO_GET_DMA failed: Invalid argument

I also tried sdparm, it's really meant for SCSI drives though and I think hdparm has support for S-ATA stuff built-in for some time now (correct me if I'm wrong).

Googling those nice errors gives some results but unfortunately they merely seem to be side effects and not the issue discussed there. If anyone had some pointers, I'd be grateful.

Last edited by B (2008-11-10 12:48:10)

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Got Leenucks? :: Arch: Power in simplicity :: Get Counted! Registered Linux User #392717 :: Blog thingy

lilsirecho

Veteran

Registered: 2003-10-24

Posts: 5,000

Re: External USB disks dog slow

I suggest that the drive(s) are slow because they are connected via USB which normally runs less than 30MB/s.

DMA enable does not improve USB performance, it is meant for HDD in an IDE port.

A sata interface will provide much improved external drive performance for sata drives.

IMHO..................

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.:B:.

Forum Fellow

Registered: 2006-11-26

Posts: 5,819

Website

Re: External USB disks dog slow

Ok... Other people told me I shouldn't expect 'performance' from USB 2 either. I'd love to go eSATA but neither my server or my laptop have any ports for this, so it's not really an option.

The only pre 2,5" HDs have is they just need the USB cable for power, nothing else. Thanks for your input

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Got Leenucks? :: Arch: Power in simplicity :: Get Counted! Registered Linux User #392717 :: Blog thingy

R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: External USB disks dog slow

If all you want is to be able to boot and use the web a 2.5'' disk on an external box will do very well. My laptop died and I'm using the disk from that laptop like that right now and there is almost no difference when compared with using it inside the laptop. Speeds around 20MB/s are very normal for the usb interface.
Here's mine:
The disk is a MAXTOR ST980215A (80G, 5400RPM, 8MB cache I think)

Bus 001 Device 003: ID 067b:2507 Prolific Technology, Inc. PL2507 Hi-speed USB to IDE bridge controller

sudo hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   1840 MB in  2.00 seconds = 920.08 MB/sec
 Timing buffered disk reads:   74 MB in  3.01 seconds =  24.60 MB/sec

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R00KIE
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