External HD questions??

***Steve*** · 04-03-2006, 20:43

I have just added extra storage to my main rig with a 300GB external HD. This will run of either USB2 or firewire and is independantly powered. I know that firewire is the quickest but as this is purely a backup drive speed is not really an issue, what I am more bothered about is connecting/disconnecting and powering it on and off. I know that USB is hot swappable so that’s no problem but whats the situation with firewire, am I to connect it and disconnect it without the pc being switched on or is it safe some other way?

Any advice please?

Warspite · 04-03-2006, 20:46

Yes - Firewire is also hot swappable, if as a precaution (as you should also do with USB devices) you stop the device through the "Safely remove hardware" tab in the system tray then power it down and unplug it, that way you should have no risk of data corruption or disconnecting while its still in use by the system.

For connection just plug it in and power it up.

***Steve*** · 04-03-2006, 21:12

Thanks you sir, you've been a great help

05-03-2006, 03:13

Basically what he said. Power down, then unplug, and the reverse for reconnection, plug in, then power up.

My DV Cam literature and Firewire card strongly advises against, hotswapping live powered devices.

***Steve*** · 05-03-2006, 08:58

Cheers gents, I think I have it sussed now

I have now got it connected by firewire (which will always be connected) but I will be powering it on and off at various times while the pc is still powered. I have altered the external drives properties to not cache any files and allow for safe removal without telling windows specifically that way if I was to forget and just powerdown there should be no errors or damage caused.

Cheers again.

Matt · 05-03-2006, 12:28

Is it a purchased external hard drive, or an icybox housing with your own HDD installed?

I've been having trouble with the icybox enclosures, ending in all data being lost on the drive. In one case it was 300G of data.
Fortunately I still had copies on the main drives in the PC.

I have two of these enclosures and have had the same problem with both.
Totally lost faith in them.

Happens when HDD switched on before PC, and off after shutdown.
Also with the safely remove hardware options.

I also have a Frrecom external HDD, and have never had a problem with it.

Glen · 05-03-2006, 12:33

Can't USB2.0 run at 480 mbps compared to firewire at 400 mbps? wouldn't it be better going USB2.0 route?

GfK · 05-03-2006, 12:38

Quote:

Originally Posted by Glen

Can't USB2.0 run at 480 mbps compared to firewire at 400 mbps? wouldn't it be better going USB2.0 route?

Not necessarily. reason being, if you have, say for the sake of simplicity, 2 USB2 devices in use at once, you only get 240mbps on each.

By comparison, if you have 2 firewire devices in use at once, you get the full 400mbps on each.

Warspite · 05-03-2006, 12:39

Quote:

Originally Posted by Glen

Can't USB2.0 run at 480 mbps compared to firewire at 400 mbps? wouldn't it be better going USB2.0 route?

True USB 2.0 can manage 480Mbps - however FireWire has a much higher sustained transfer rate, whereas USB 2.0 only peaks at 480Mbps.

Glen · 05-03-2006, 12:43

Oh I see..........I'll shut up now then........

SammyC · 05-03-2006, 13:31

Yes, shut up!

mrgubby · 05-03-2006, 14:13

SATA150 is 'only' 150Mbs so USB2 and Firewire are both probably faster than the drive

Warspite · 05-03-2006, 14:16

Dont confuse Mbps (Mega bits) with MBs (MegaBytes).

Its takes 8 bits to make 1 byte

SammyC · 05-03-2006, 14:37

Actually it usually works out to be 10 bits in a byte, on a serial comms link the protocol overhead adds roughly 2 bits per byte.

I.e. a 512 kBITSps == 50 kBYTESps.

GfK · 05-03-2006, 14:44

Quote:

Originally Posted by SammyC

Actually it usually works out to be 10 bits in a byte, on a serial comms link the protocol overhead adds roughly 2 bits per byte.

I.e. a 512 kBITSps == 50 kBYTESps.

But a byte is and will always be 8 bits, not 10 regardless of 'overhead'. A byte can hold any value between 0 and 255. 0 expressed as binary is %00000000, while 255 is %11111111.

1 = %00000001
2 = %00000010
3 = %00000011
4 = %00000100
5 = %00000101
6 = %00000110
7 = %00000111

...and so on.

Warspite · 05-03-2006, 14:51

Agree - it may add 2 bits, but a byte is still 8 bits, just as a nibble is 4, and so on - what your describing sounds to me more like a "word", however Im no expert on serial comms.

However a byte is in most cases - ie networking, performance measurement, always expected to contain 8 bits.

GfK · 05-03-2006, 14:55

Quote:

Originally Posted by Warspite

Agree - it may add 2 bits, but a byte is still 8 bits, just as a nibble is 4, and so on - what your describing sounds to me more like a "word", however Im no expert on serial comms.

However a byte is in most cases - ie networking, performance measurement, always expected to contain 8 bits.

Well, a byte *is* 8 bits. There's really no discussion to be had

If you need to send 10 bits then you need to be sending a 'word' (2 bytes). But then you're effectively sending 6 redundant bits because you can only transmit whole bytes. I don't wanna get into the realms of bit-shifting/compression to get around that problem, so we should probly go back to the original topic now.

04-03-2006, 20:43	#1 (permalink)
*Steve* Pixalo Crew Join Date: Jan 2005 Location: An Englishman living in Germany Posts: 16,468	External HD questions?? I have just added extra storage to my main rig with a 300GB external HD. This will run of either USB2 or firewire and is independantly powered. I know that firewire is the quickest but as this is purely a backup drive speed is not really an issue, what I am more bothered about is connecting/disconnecting and powering it on and off. I know that USB is hot swappable so that’s no problem but whats the situation with firewire, am I to connect it and disconnect it without the pc being switched on or is it safe some other way? Any advice please? __________________ .......__o .......\<, ....( )/ ( )

05-03-2006, 14:16	#13 (permalink)
Warspite Feet under the table Join Date: Sep 2005 Location: Newcastle Sunderland Middlesbrough (UK) Posts: 1,736	Dont confuse Mbps (Mega bits) with MBs (MegaBytes). Its takes 8 bits to make 1 byte Last edited by Warspite : 05-03-2006 at 14:23.

04-03-2006, 20:46	#2 (permalink)
Warspite Feet under the table Join Date: Sep 2005 Location: Newcastle Sunderland Middlesbrough (UK) Posts: 1,736	Yes - Firewire is also hot swappable, if as a precaution (as you should also do with USB devices) you stop the device through the "Safely remove hardware" tab in the system tray then power it down and unplug it, that way you should have no risk of data corruption or disconnecting while its still in use by the system. For connection just plug it in and power it up.

04-03-2006, 21:12	#3 (permalink)
*Steve* Pixalo Crew Join Date: Jan 2005 Location: An Englishman living in Germany Posts: 16,468	Thanks you sir, you've been a great help

05-03-2006, 03:13	#4 (permalink)
Marcel Posts: n/a	Basically what he said. Power down, then unplug, and the reverse for reconnection, plug in, then power up. My DV Cam literature and Firewire card strongly advises against, hotswapping live powered devices.

05-03-2006, 08:58	#5 (permalink)
*Steve* Pixalo Crew Join Date: Jan 2005 Location: An Englishman living in Germany Posts: 16,468	Cheers gents, I think I have it sussed now I have now got it connected by firewire (which will always be connected) but I will be powering it on and off at various times while the pc is still powered. I have altered the external drives properties to not cache any files and allow for safe removal without telling windows specifically that way if I was to forget and just powerdown there should be no errors or damage caused. Cheers again.

05-03-2006, 12:28	#6 (permalink)
Matt Member Join Date: Jan 2005 Location: Cheshire Posts: 1,326	Is it a purchased external hard drive, or an icybox housing with your own HDD installed? I've been having trouble with the icybox enclosures, ending in all data being lost on the drive. In one case it was 300G of data. Fortunately I still had copies on the main drives in the PC. I have two of these enclosures and have had the same problem with both. Totally lost faith in them. Happens when HDD switched on before PC, and off after shutdown. Also with the safely remove hardware options. I also have a Frrecom external HDD, and have never had a problem with it.

05-03-2006, 12:33	#7 (permalink)
Glen Been here a while Join Date: Feb 2006 Posts: 333	Can't USB2.0 run at 480 mbps compared to firewire at 400 mbps? wouldn't it be better going USB2.0 route?

05-03-2006, 12:43	#10 (permalink)
Glen Been here a while Join Date: Feb 2006 Posts: 333	Oh I see..........I'll shut up now then........

05-03-2006, 13:31	#11 (permalink)
SammyC Forum Regular Join Date: Jul 2005 Location: Bristol Posts: 1,466	Yes, shut up!

05-03-2006, 14:13	#12 (permalink)
mrgubby Been here a while Join Date: Nov 2005 Location: Hertfordshire Posts: 328	SATA150 is 'only' 150Mbs so USB2 and Firewire are both probably faster than the drive

05-03-2006, 14:37	#14 (permalink)
SammyC Forum Regular Join Date: Jul 2005 Location: Bristol Posts: 1,466	Actually it usually works out to be 10 bits in a byte, on a serial comms link the protocol overhead adds roughly 2 bits per byte. I.e. a 512 kBITSps == 50 kBYTESps.

05-03-2006, 14:51	#16 (permalink)
Warspite Feet under the table Join Date: Sep 2005 Location: Newcastle Sunderland Middlesbrough (UK) Posts: 1,736	Agree - it may add 2 bits, but a byte is still 8 bits, just as a nibble is 4, and so on - what your describing sounds to me more like a "word", however Im no expert on serial comms. However a byte is in most cases - ie networking, performance measurement, always expected to contain 8 bits.

05-03-2006, 15:00	#18 (permalink)
Warspite Feet under the table Join Date: Sep 2005 Location: Newcastle Sunderland Middlesbrough (UK) Posts: 1,736