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16  Linux Stuff / General Linux questions / Re: Storage for Database on: December 11, 2010, 06:18:19 AM
Personally, I'd think your primary consideration would be the size of the database, and a secondary one would be read-to-write ratio.

If the database is small enough to fit on an SDcard, I'd try that first.  Buy a fast one, and reads will probably be faster than a hard drive.  After all, you have no rotational delay to contend with.  And, they're building solid state hard drives now -- NAND memory packaged to look like a disk drive with a SATA interface -- so with active whitening, NAND has become quite robust with respect to tolerating write cycles.  If you need the space, or have an application with enough writes to make write timing an issue, choose a HD.  I would personally stay away from using the internal NAND for this task -- I don't think it is as fast, and it's not replaceable.

My two cents.
17  Hardware and U-Boot firmware / Hardware / Re: SheevaPlug memory lifetime in production environment on: December 10, 2010, 12:39:30 PM
If you specify both relatime and noatime, I'm not sure what will happen.  Perhaps the last one mentioned will take effect; perhaps the more stringent one (noatime) will.  My reading of the man page is that these parameters affect both files and directories.  The diratime and nodiratime parameters affect only directories, but not files.  (It's unclear whether "noatime,diratime" could be specified to update directories, but not files.  My guess is no.)

If this interests you, why not play around with these parameters and post the results.
18  Hardware and U-Boot firmware / Hardware / Re: SheevaPlug memory lifetime in production environment on: December 08, 2010, 10:10:14 PM
Essentially correct for "relatime" (not "realtime").  See http://linux.koolsolutions.com/2009/01/30/installing-linux-on-usb-part-4-noatime-and-relatime-mount-options/

I use "relatime" on several ext2 file systems, root and otherwise.  It works for all ext type file systems.  Not sure about other fs types.
19  Hardware and U-Boot firmware / Hardware / Re: SheevaPlug memory lifetime in production environment on: December 08, 2010, 08:35:35 PM
'noatime' simply inhibits the update of the inode's timestamp on access for ext* file systems.  It thus cuts down on the number of writes to the filesystem.  However, it does create some problems.  A common one is the inability to discern whether or not you have new mail.  (It tends to always look like you do.)  I use 'relatime', which allows an inode update if the current access time on a file is older than the current modification time.  This solves most of the timestamp problems, while still cutting down on file system writes, sometimes significantly.

FWIW, I've had a SheevaPlug that has been running 24/7 since Sept 2009 on an SDcard root file system.  Except for 'relatime', I've made no attempt to curb file system activity, and the SDcard continues to perform fine.  I really suspect the SDcards made today are quite capable of supporting an active Unix file system for an extended period without the risk of burn out.  I must confess, though, if I were using the SheevaPlug's internal NAND, I 'd probably be a bit more concerned about this, since it is not easily replaceable.

20  Hardware and U-Boot firmware / Hardware / Re: Is there really a major problem with the GuruPlug? on: December 06, 2010, 11:17:01 PM
My GuruPlug did not run any hotter than my SheevaPlug with WiFi and one 100Mbit ethernet connection active.  I never tried connecting it to a Gbit ethernet, but I understand those who did complained that the RJ45 jack did become quite hot.  Perhaps others who have tried it can be more specific.

For more information, see:

21  Hardware and U-Boot firmware / Hardware / Re: Is there really a major problem with the GuruPlug? on: December 06, 2010, 06:26:18 PM
The conventional wisdom is that the RJ45 run HOT when connected to a Gigabit ethernet network.  Those who run it connected to 100 Mbit networks say it doesn't exhibit these symptoms.  While I owned a GuruPlug, I ran it on a 100 Mbit network and it seemed to put out about the same amount of heat as my SheevaPlug.  It got warm, but I wouldn't have burned my fingers on it.  YMMV.
22  Linux Stuff / Kernel / Re: and new kernels available on: December 05, 2010, 10:54:47 AM
A minor nit:  I haven't updated my kernel recently, but did so last night in order to get iotop to work.

Sometime in the past year, or at least since (see how far behind I was?), the packaging of the Modules tar file has been changed set the group write flag on all directories touched, which includes /, /lib, /lib/modules, etc.  Since the ownership of these directories are all root/root, this does not present a security problem.  However, the changing of the permissions on / (the root directory) breaks sendmail, which by default requires all its sensitive directories to not be group writeable.  Thus, it breaks mail delivery.

Would it be possible to change future kernel loads so as to avoid setting group write permission on these directories?

BTW, seemingly works fine in other respects.  Now, iotop works for me, and I have noticed no other anomalies.  I do wonder, though:  Just how far can I push things as far as running the latest kernels on a Ubuntu 9.04 load?  When will things start to break?  (I suppose I mean, when will the kernel/user interface start to change?  Does it only do so on major generic boundaries, such as the transition from 2.6 to 2.7?)

And, thanks again, cbxbiker61, for your continuing kernel support.
23  Hardware and U-Boot firmware / Hardware / Re: My Modified SheevaPlug part II on: December 01, 2010, 02:40:56 PM
Just a head's-up:  Over in the Jeff Doozan Dockstar, they are modifying Nokia CA-42 data cables to interface with the 3.3V serial logic on the Dockstar's board.  Perhaps that would be an easy solution here, too.
24  Hardware and U-Boot firmware / Hardware / Re: Poll: What is the status of your SheevaPlug's Power Supply? on: November 30, 2010, 08:49:56 PM
It likely is just a bad power supply.  Have you disassembled it and measured the PS voltage?  If it turns out to be that, it is fairly easy to replace with a 5V 2A wall wart.

Good luck.
25  Hardware and U-Boot firmware / Hardware / Re: "Official" replacement PSUs - anyone had one? on: November 26, 2010, 07:11:26 PM
Thanks chomeur.  Out of curiousity, what were the shipping costs?
26  Hardware and U-Boot firmware / U-Boot stuff / Re: Questions regarding nand and u-boot partitions on: November 18, 2010, 01:07:06 PM
That's a good bit of information to know.  Thanks.
27  Hardware and U-Boot firmware / Hardware / Re: Guruplug I/O and JDB errors on writing to micro SD card on: November 17, 2010, 10:54:43 PM
I can't comment on whether any data got lost.  I do think Unix tends to retry such errors, but I would at least do an "fsck -f" on the affected partitions -- and preferably from an external machine when you fsck your root partition.

That said, I will mention that I got some similar errors once from my SheevaPlug, and pulling and reseating the SD-card a few times cured it.  Sometimes the contacts develop some resistance over time.  You might want to try that on your Guruplug.
28  Hardware and U-Boot firmware / U-Boot stuff / Re: Questions regarding nand and u-boot partitions on: November 17, 2010, 01:56:58 PM
However, to be clear, the kernel image has to be compiled for a specific initial memory location, right?  (In other words, it's not compiled entirely of relatively addressed code.)
29  Hardware and U-Boot firmware / Hardware / Re: Another dead one? on: October 29, 2010, 06:01:14 PM
Yes, I have a spare 5V 3A power brick sitting on the shelf, just in case.  It's really a very handy thing to have for a number of reasons.

As far as WiFi, I'm sure there are some USB devices that could be made to work, but also consider the GuruPlug line, which comes with built-in WiFi hardware.
30  Hardware and U-Boot firmware / Hardware / Re: Another dead one? on: October 29, 2010, 01:51:41 PM
Hi CqCn,
Sorry for the late reply.  I've been out of town myself this past week.

I'm still running on my original unmodified power supply.  I only have one Plug, and it's in service, so I've been hesitant to open it up and experiment.  A friend's PS did bite the dust recently and I have that defective PS board in my possession.  Unfortunately, he tried to fix it first, and I don't have all the caps he removed, so I can't give you a definitive list.  Perhaps someone else on this forum can help.

From what I've read (and my friend's personal experience), it is fairly easy to convert the Plug to an external PS.  You just need a well filtered 5V DC 2A brick.  There is a single connector between the PS board and the processor board, and you can feed the power to the processor from this connector.  A side benefit of using an external supply is that the Plug then runs quite cool.  Apparently most of the heat generated comes from the internal PS.

I have one other thing I'm curious about:  Has anyone ever opened up their Plug and examined the PS after it has been running for a while, but before the PS fails?  I notice a lot of folks think the gunk the find spread all over everything after the PS fails is due to one or more capacitors leaking electrolyte over the board.  But people I've shown the defective PS to who know all about capacitor plague tell me what is on the failed board looks nothing like any capacitor leakage they've seen.  It's a hard, dry substance, not wet electrolyte, and it doesn't appear to emanate from any capacitor.  I personally wonder if what we are seeing is dried glue put on as part of the manufacturing process, perhaps darkened by the heat over time as the PS has run.  If someone can shed some more light on this, I'd be interested.

Welcome back, CqCn.  Let us know when you get your Plug up and running.
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