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 Forum index » House Training » Users ( For the regulars )
USB hard disk - is it safe to simply plug ang unplug it?
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raffy

Joined: 25 May 2005
Posts: 4843
Location: Manila

PostPosted: Mon 07 May 2007, 19:54    Post subject:  USB hard disk - is it safe to simply plug ang unplug it?  

USB-connected external hard disk enclosures are common today, so you can simply plug and unplug the hard disk via its USB connector. My concern is whether this manner of using the drive is harmful to the drive when done repeatedly. I was taught sometime ago that a hard disk is supposed to be "parked" at shutdown time of a PC. Is this still the preferred procedure in unplugging a hard drive? If so, how could this be done?

Of course connecting the drive at bootup and unplugging it at shutdown should be best, but am thinking of a portable hard drive like a 2.5" disk that is plugged or unplugged to a PC when needed.

Thanks for your help.

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Béèm


Joined: 21 Nov 2006
Posts: 11775
Location: Brussels IBM Thinkpad R40, 256MB, 20GB, WiFi ipw2100. Frugal Lin'N'Win

PostPosted: Mon 07 May 2007, 20:28    Post subject:  

In any case umounting should be done first to avoid corruption of the file system and be sure all data is written to the device.

Then I am guessing that unpluging (thus cutting power) will result in a parking condition. May depend on the brand used.

I have such a device, altho powered externally, and have had no problems yet. It even fell recently by accident from a low table and still works ok.
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paulsiu

Joined: 16 Jan 2007
Posts: 187

PostPosted: Mon 07 May 2007, 20:36    Post subject: flushing  

When you unmount the drive, it flushes the unwritten data to the hard disk. If you just unplug the drive, it may or may not contain unwritten data. If you just written something to disk and immediately unplug it, some data may be lost or damaged.
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Gn2


Joined: 16 Oct 2006
Posts: 936
Location: virtual - Veni vidi, nihil est adpulerit

PostPosted: Mon 07 May 2007, 21:09    Post subject:  

Raffy

Think about the reason to use such a device > USB - MADE to be portable/externally pluggable
Then consider - Puppy has trouble even accessing some devices for normal usage

Where did you get your info on "Parking" ~ you do realise it refers to controlling the drive heads.

That requires direct kernel DMA access to device - through a M/Brd bus controller.

NOT a common user ability - there is an old (hex , NOT text) utility to park drive device heads .

It is very small, once useful , no longer (new drive specs)
Very popular little program- but NOT for intended purposes !

Modified & embedded as E.G. a graphical Url. it will destroy user's drive.

http://www.ackadia.com/computer/system-architecture/system-architecture-harddrive.php

BTW whether the drives' buffers are flushed or not depends on how sytem was Cfg'd -
Asyncronous write through, vs normal Cpu cycle interupt queued writes - how often saved back to disk.

http://lwn.net/Articles/216200/
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Gn2


Joined: 16 Oct 2006
Posts: 936
Location: virtual - Veni vidi, nihil est adpulerit

PostPosted: Mon 07 May 2007, 21:43    Post subject:  

This may be interesting to you:

HARDWARE

Aside: the latest "device drivers - vulnerable to malware" scare ,
such as vid drivers etal -
Are hardly new - any low level hardware DMA access poses that possibility.
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raffy

Joined: 25 May 2005
Posts: 4843
Location: Manila

PostPosted: Mon 07 May 2007, 22:39    Post subject: clarification  

Thanks for the quick response, guys. Let me clarify that the drive is already unmounted, it is just the act of disconnecting and thus cutting off power that worries me (and should worry other users, too).

Yes, my concern is about the heads, as if not parked, this would easily expose the drive to damage when moved about.

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GuestToo
Puppy Master

Joined: 04 May 2005
Posts: 4078

PostPosted: Mon 07 May 2007, 23:21    Post subject:  

i agree with the other posters ... you do not need to park a newer hard drive

see here
Quote:
modern hard disks will automatically park their heads--even in the event of a power failure--and no utilities are required
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raffy

Joined: 25 May 2005
Posts: 4843
Location: Manila

PostPosted: Tue 08 May 2007, 01:08    Post subject: thanks  

Thank you very much for the information!

Now a diskless Puppy machine will be easy to backup anytime with a portable USB hard disk (small hard disk in USB-connected enclosure).
usb_hard_drive.jpg
 Description   small hard disk in $12 USB enclosure
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usb_hard_drive.jpg


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slvrldy17

Joined: 17 Feb 2006
Posts: 292
Location: Mid western USA

PostPosted: Tue 08 May 2007, 09:20    Post subject: USB Drives  

Have been using both portable USB hard drives USB keys longer now than I've been working with Puppy - (Has it been THAT long?) - and never a problem with data loss when moving them. The most important thing is to remember to unmount the drive before unplugging it - not so much for the sake of the drive heads as it is to prevent loss of any data being written to the drive. Improvements to MUT in the last year or so have made this quick and easy - haven't had any problems with detecting USB keys/drives in quite some time now. Have a couple of small drives made up off of old notebook drives - one of 4.75GB and one of about 18GB and they are very useful indeed - I use them to transfer/carry files I'm working on for my church. I use larger ones for general backup of my music, pictures, etc.
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Dougal


Joined: 19 Oct 2005
Posts: 2504
Location: Hell more grotesque than any medieval woodcut

PostPosted: Tue 08 May 2007, 15:47    Post subject: Re: USB Drives  

slvrldy17 wrote:
Have been using both portable USB hard drives USB keys longer now than I've been working with Puppy - (Has it been THAT long?) - and never a problem with data loss when moving them.


You seem like you're volunteering to run my HW-test dotpup to help we find out how the removable HD is recognized...
HW-test.pup
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pup

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Filename  HW-test.pup 
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Béèm


Joined: 21 Nov 2006
Posts: 11775
Location: Brussels IBM Thinkpad R40, 256MB, 20GB, WiFi ipw2100. Frugal Lin'N'Win

PostPosted: Tue 08 May 2007, 18:28    Post subject:  

Dougal,
Please find the info of my Medion MD8818 PC, the one with the sata HDD not being recognized.
Maybe it is of use for you.
results-Béèm.MD8818.tar.gz
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raffy

Joined: 25 May 2005
Posts: 4843
Location: Manila

PostPosted: Tue 08 May 2007, 19:47    Post subject: Test Results - 2 machines  

Tested on two machines: one with Celeron/SiS and another with AMD GX466 (thin client).
raffy-results.zip
Description  results for gx466 and sis620 chips
zip

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Dougal


Joined: 19 Oct 2005
Posts: 2504
Location: Hell more grotesque than any medieval woodcut

PostPosted: Wed 09 May 2007, 09:24    Post subject:  

Thanks guys.

Raffy: did you have a removable HD connected to any of them?

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raffy

Joined: 25 May 2005
Posts: 4843
Location: Manila

PostPosted: Wed 09 May 2007, 18:20    Post subject: yes  

Yes, with multiple partitions:
sda1 - ext2
sda2 - swap (not used)
sda3 - ext2
sda4 - ext2
for 40 GB total storage.

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twodees

Joined: 03 Apr 2007
Posts: 50

PostPosted: Wed 09 May 2007, 22:01    Post subject:  

I wondered about that too when using my usb drive with puppy. I think it's because XP used to warn me not to remove the drive without clicking on their command which was supposed to prepare the drive for safe removal. Maybe XP automatically mounts the drive when it's detected, I don't know. Windows does so many things without letting the user know what's being done.
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