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Author Topic: Choosing a USB powered hard drive for the Sheeva  (Read 8623 times)
monkeyhybrid
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« on: December 16, 2009, 09:32:42 AM »

I took receipt of my first Sheevaplug today and intend to have some serious play time over the xmas hols! Smiley

My plan is to hook up a USB2 portable drive to it, ideally bus powered via the Sheevaplug's USB rather than needing it's own seperate PSU. 320GB+ 2.5" is afforable and would be nice and I would favour low power and reliability over performance. It will become my home office file / mail / web / svn server with relatively light use. Does this seem like a reasonable way to go?

Any known problems with the Sheevaplug powering USB drives or advice on particular drives to go for?

Any reason I shouldn't install the OS on the USB drive? I figured it would be more reliable than flash/SD and less to worry about in terms of max writes...

In terms of spinning down, will all USB drives spin down after a set period of time or would this have to be configured in drive firmware by connecting the bare drive to a PC's SATA connection and using manufacturer's diagnostic tools. The mail server will probably be storing mail every few minutes, so maybe it's not a good idea for it to spin down at all?

Would it be advantageous to get a USB to SATA adapter and run the drive as a eSATA drive? I know it would not be any faster due to the USB bottleneck, but would it lallow me to use S.M.A.R.T., etc?

Any advice would be much appreciated! Smiley


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fragfutter
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« Reply #1 on: December 16, 2009, 10:18:51 AM »

usb ports are rated with 500mA max. The sheeva delivers something around 700mA. Most 2.5" USB Harddisks require two USB sockets and draw around 600mA. So yes they work on the Sheeva.

Having the root-fs on flash/sd makes it easier for the USB Disk to spin down. For example your syslog will normaly write at least the heartbeat. This can be tuned, but you will always find something that wants to write Wink

Not all harddisks spin down. There are some that do powermanagement by themself, some that allow to do it through the system and some that don't spin down at all. I can't name a brand. I personally have a Maxtor One Touch 320GB and it does the spindown. I know of quite a bunch of Western Digitals that also do it.

The USB/eSata way won't bring you any advantages. you can read s.m.a.r.t. over usb.

i have an 8GB SD card with the system and files that get regular access and a USB for bulk storage (NFS shares). Harddisk will spin down when i'm not at home/using the NFS. I would not use spindown with mailspool or web. The delay on first access is noteable and you would get a high load-cycle count which could damage the disk.
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monkeyhybrid
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« Reply #2 on: December 16, 2009, 10:42:15 AM »

Thanks for the very useful information!

With regard to using the 8GB SD for root filesystem, have you had any issues at all? I was initially planning on doing that but was worried about excessive writes to the SD card causing it to fail prematurely. It would be nice if I could let the USB drive spindown overnight or whilst I'm away.

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DamonHD
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« Reply #3 on: December 16, 2009, 11:32:41 AM »

I'm using a 128GB (not MB) USB thumbdrive for bulk storage for one particular application of mine, and clearly power consumption from USB is then not a make-or-break issue.

But beware: if you care about power consumption and use a USB hub then the hub won't power down automatically since the kernel doesn't know when it can suspend media devices, which then in turn wastes significant power in the hub and through CPU wakeups.

My plug also has a 32GB SD card for large partitions such as /home, and I boot from NAND, so I apply multiple strategies to reduce write load.

http://www.earth.org.uk/note-on-SheevaPlug-setup.html

The previous system used a 4GB SD card for booting/root and, using similar strategies, showed no sign of write stress over the course of a year or more.

Rgds

Damon
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monkeyhybrid
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« Reply #4 on: December 16, 2009, 12:21:24 PM »

Thanks for the advice Damon. Great link too, will be reading that properly in a few mins.

I'm just about to order a Seagate FreeAgent Go 500GB (http://www.ebuyer.com/product/149451) which will do me nicely for storage and I think I have some SD cards around here I'll play with too.

Cheers!
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monkeyhybrid
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« Reply #5 on: December 16, 2009, 12:33:46 PM »

Ahhh, I just read that the SheevaPlug can not provide the Seagate FreeAgent series of hard drives with enough power so an external PSU must also be used. From the SheevaPlug WIKI: http://www.plugcomputer.org/plugwiki/index.php/Frequently_Asked_Questions#Can_I_Use_a_Seagate_USB_FreeAgent_Go_250_GB_or_Similar_Large_USB_Drive.3F

So, won't be buying that drive...
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DamonHD
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« Reply #6 on: December 16, 2009, 12:42:59 PM »

Go to the dark side and get USB flash if you can afford it!  B^>

(Crusty old UNIX apple anecdote alert: my USB thumbdrive has about 100x the storage capacity that my entire uni had across all departments and campuses when I was a first-year student!)

Rgds

Damon
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monkeyhybrid
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« Reply #7 on: December 16, 2009, 01:22:18 PM »

That would be nice, bit more than I was hoping to spend though Wink

Just going to do some research on external USB drive power consumptions, find a good model to buy.

Will let you know how I get on!
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fragfutter
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« Reply #8 on: December 16, 2009, 02:10:00 PM »

With regard to using the 8GB SD for root filesystem, have you had any issues at all? I was initially planning on doing that but was worried about excessive writes to the SD card causing it to fail prematurely. It would be nice if I could let the USB drive spindown overnight or whilst I'm away.

no issues. Running for about five months.

My harddisk is on a powered USB hub, it poweres my charging craddles for various USB stuff (mobile phone, ps-controller, ipod dock, ...) so i would have the USB hubs Power-Supply plugged in anyway.
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Hamster
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« Reply #9 on: December 16, 2009, 07:27:07 PM »

I've had really good luck with the old style Western Digital My Passport Essential drives (http://www.newegg.com/Product/Product.aspx?Item=N82E16822136228). I am running a 160GB on my first Sheeva (~6 months uptime) and running a 250GB on my second Sheeva (~3 months uptime).

Sheeva1 is currently running a web, FTP, and Twonky media server to stream to my Xbox360. I would say it is used for about 12+ hours out of the day. Sheeva2 is a file/backup server for backing up a couple laptops and desktops, and is used about 4 hours a day.

Dell has a good deal on a 320GB with free shipping for $60 (http://accessories.us.dell.com/sna/productdetail.aspx?c=us&cs=04&l=en&sku=A3037330) I don't have this particular drive model, so I am not sure if it works as well as the others, but would imagine it would.
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monkeyhybrid
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« Reply #10 on: December 17, 2009, 05:45:03 AM »

no issues. Running for about five months.

That's good, but I still can't shake this feeling of impending doom! I've had a few SD cards fail on me in the past (usually in cameras) so maybe I've been burnt more than others. I'll have to ask you again in a few months time and maybe that will be persuade me to cross over.

At the moment, I figure the USB hard drive on my setup will be spinning majority of the day, if not 24/7, so it may as well host the OS along with everything else.

I've had really good luck with the old style Western Digital My Passport Essential drives (http://www.newegg.com/Product/Product.aspx?Item=N82E16822136228). I am running a 160GB on my first Sheeva (~6 months uptime) and running a 250GB on my second Sheeva (~3 months uptime).

Thanks. I've actually just ordered a Western Digital My Passport Essential 500GB! Will let you guys know how I get on with it. Probably best if we add results of all these hard drives in the external hard drive section of the Plug Computer WIKI.
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mhtsaras
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« Reply #11 on: December 28, 2009, 05:26:52 AM »

...
Thanks. I've actually just ordered a Western Digital My Passport Essential 500GB! Will let you guys know how I get on with it. Probably best if we add results of all these hard drives in the external hard drive section of the Plug Computer WIKI.

So monkeyhybrid what are the news?
The Western Digital My Passport Essential 500GB can work with only the usb power of the plug? or it needs an extra usb hub?
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monkeyhybrid
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« Reply #12 on: December 28, 2009, 03:28:25 PM »

Yes, I can confirm the Western Digital My Passport Essential 500GB drive works with the Sheevaplug, being powered soley from the Sheeva's USB port. Smiley

I havn't done much with it yet but will do more over next few days. So far I've just plugged it in, mounted it, and read files from it.

One thing to note with these WD drives, is that they come with a virtual CD drive setup, so that once plugged in, special WD encryption drivers and utilities are made available to any Windows PC that needs them. I downloaded a tool from their site to disable this.

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mhtsaras
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« Reply #13 on: December 29, 2009, 07:15:32 AM »

I'm glad that it works with the Sheevaplug, but the strange thing is that in this page from Western Digital Knowledge Base -->
http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_adp.php?p_faqid=1731
says that "Drive Maximum Power Draw (milliamps) 1000 Ma " and the Sheevaplug goes to usb output max=780 mA
It seems like if you stress the disk, the sheevaplug's usb power, won't have enough juice to feed the drive so maybe sometime you will have a problem.
Considering that the max output of the plug is 780 mA, I was going to buy a WD PASSPORT (not MY PASSPORT) with 320GB (WD3200U017, WDXMSA2500, WDXMSB2500, WDXMSC2500, WDXMSE2500) which needs "Drive Maximum Power Draw (milliamps) 650 Ma" as it says in that page --> http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_adp.php?p_faqid=1555
But after your last post saying that My Passport Essential 500GB, works with the sheevaplug I don't know what to do.
Maybe some experts here in the forum that have more knowledge about the sheevaplug hardware capabilities will give us their opinion.

The stupid hard disk companies say that the drives are usb compatible but the usb specification for power --> http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power   says that "A unit load is defined as 100 mA in USB 2.0, and was raised to 150 mA in USB 3.0. A maximum of 5 unit loads (500 mA) can be drawn from a port in USB 2.0, which was raised to 6 (900 mA) in USB 3.0.is under 500 mA "
So making usb devices that draw so much (650 or 1000 mA) that the provided usb power from a pc or a plug can not reach, are not usb compatible in my book...
For those who want to see the specifications of Western Digital passport portables and their disks click this link --> http://support.wdc.com/product/kb.asp?level1=2&lang=en

« Last Edit: December 29, 2009, 07:34:42 AM by mhtsaras » Logged

monkeyhybrid
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« Reply #14 on: December 29, 2009, 08:51:34 AM »

Hmmm, I had had a quick look around for details such as that, but obviously not as thoroughly as yourself!

I think maybe the figure of 1000mA may refer to the max output of an optional AC adapter that comes with some models and not actually the expected consumption of these drives, but can't be sure. The model I have doesn't even have the option of being connected to an AC adapter, or even to a 'double' USB lead as some models do, so it would seem daft if this drive would ever need much more than 500mA.

If you find any further info on this, I'd love to hear it. When I have some spare time, maybe tonight, I'll do some more intensive tests with continuous reading and writing to the drive and let you know how it went.
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