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Old 12-11-2012, 04:58 AM   #16
fotoguy
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Quote:
Originally Posted by geox View Post
Ah, much like running from a LiveCD then
Yeah the same as a livecd. Root system on the SSD will always be read-only, you'll be able to add things like software, or change configuration files. e.g. your email settings, if you download to your home directory, music movies etc.. they will all be written to the read-write branch which will point to your HDD, so they will be there when you reboot.
 
Old 12-11-2012, 05:50 AM   #17
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Still, it all seems a bit overcomplicated to solve the problem of failing SSD's...
 
Old 12-11-2012, 07:20 AM   #18
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Quote:
Originally Posted by geox View Post
A ramdisk is faster and reduces wear on your SSD but considering the very minor performance increase, the fact SSD's are optimized to reduce wear already and the drawbacks mentioned I'd say this setup has advantages for very few setups/uses. Compiling 3-4 linux kernels a day is one of those uses.
Exactly, and not even in this particular use case I would consider it worth to spend the time to configure the system to have the rootfs in RAM. Machines that are used for that purpose usually have plenty of RAM and can simply mount tmpfs to the directory that is used for compiling.
 
Old 12-11-2012, 09:06 AM   #19
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Quote:
Originally Posted by fotoguy View Post
Sorry I should have made myself a little clearer with replica9000 post, people may not familiar with unionfs filesystems. Aufs creates branches, which are read-only, and read-write, with live cd/dvd which use unionfs filesystems, the read-write branch is usually on a ramdisk, which will be lost on reboot/restart, but in replica9000 situation using a hdd which is read-write, you could just create a read-write branch that would point to the hdd, so any modification are made dynamically and would not be lost on reboot/restart. Not sure how easy this would be to do, haven't done it myself, but i'm looking into something like this myself for a bit of experimentation.
I have used Aufs via fsprotect when I setup a lightweight usb install. Instead of creating a livecd image, it allows me to have a typical install either behave as normal, or behave like a livecd. All I had to do was specify an extra boot option, set in grub.


Quote:
Originally Posted by geox View Post
If an embedded system uses RAM as a rootfs they implement a lot of workarounds to get it to work consistently. This is not easy to do. If you put your rootfs in RAM be aware of these drawbacks. You WILL lose changes. You will gain speed, but due to disk caching in Linux this will be minimal.
I would agree read speeds are minimal improvement in real world performance, write speeds are definitely noticeable, usually during software upgrades.


Quote:
Originally Posted by TobiSGD View Post
Exactly, and not even in this particular use case I would consider it worth to spend the time to configure the system to have the rootfs in RAM. Machines that are used for that purpose usually have plenty of RAM and can simply mount tmpfs to the directory that is used for compiling.
For me it's just for the fun of experimenting. It really wasn't difficult to setup at all. And it's simple to switch back to running off of the SSD by choosing the original initrd.img at boot.
 
Old 12-11-2012, 12:55 PM   #20
fotoguy
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Quote:
Originally Posted by geox View Post
Still, it all seems a bit overcomplicated to solve the problem of failing SSD's...
Yeah it is a bit over the top, something I just thought would be great to experiment with.
 
  


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