I suddenly need some ram for a HTPC build, and I really want to poach the low profile 1GB sticks in my Unraid box. The only replacements I have at the current time are two 256mb sticks. I use no add ons- is 512mb enough?

 

EDIT: Thinking about it, I could also take one of my 1GB sticks from my older server so each has 1GB of RAM. Would that work?

unRAID runs in 512MB fine...

unRAID runs in 512MB fine...

 

Will the 5.0 work within a gig with only lite add ons (like Unmenu type add ons, not ps3mediaserver type add ons)?

I haven't looked to see how much ram it uses when running, but it shouldn't be drastically larger. The 5.0b2 bzroot is maybe 1 Meg larger than 4.5.6 (54 vs 53 Meg). However, during the 5.0 beta there could be a switch to Slackware 13.x as the base and more kernel modules are being made available to handle power management and importing data from ext3/ext4 drives, so it may grow a little bit more.

It should work file with 512MB of ram, albeit at the cost of cached data.

You may need to tune the kernel if it starts getting out of memory errors.

I had to adjust sysctl vm.vfs_cache_pressure=

to a higher value. I had 4GB of ram but I ran a daily updatedb on the whole system and it would cause me to run out of ram.

 

The default is

vm.vfs_cache_pressure = 10

I raised mine to 100 and above.

 

For now I would leave everything alone. if you have OOM errors, then adjust this value.

 

Also, although the prior post mentions the size of the bzroot is slightly larger.

Consideration must be given to emhttp and what ever temporary memory it may require to run php for template processing.

 

Keep an eye on the syslog., in most cases without any addons you will be fine.

unRAID should run fine, but you most likely will lose the ability to preclear 2 TB drives.  1 GB or more of RAM is required to preclear 2 TB (or presumably larger) drives.

 

If you have the option of using a 1 GB stick instead (even if it is slow), I would recommend it just for this reason.

unRAID should run fine, but you most likely will lose the ability to preclear 2 TB drives.  1 GB or more of RAM is required to preclear 2 TB (or presumably larger) drives.

 

If you have the option of using a 1 GB stick instead (even if it is slow), I would recommend it just for this reason.

 

I don't think it's the pre-clear operation that will be lost. That takes a minimal amount of ram.

 

What will cause issues is when giant drives are very full and something happens to the reiserfs requiring a reiserfsck.

There have been reports of reiserfsck failing because of memory exhaustion.

I could have sworn I read about some user having problems with that, but I can't find anything now so maybe you are right.  Joe L. would know.

 

Either way, this sounds like the best course of action to me:

 

Thinking about it, I could also take one of my 1GB sticks from my older server so each has 1GB of RAM. Would that work?

So one gig is certainly enough? Like no matter what (with no add ons)?

Absolutely (as of Aug 25 2010 ).

The ONLY issue I am aware of with 512Meg of RAM is that a reiserfsck of a 2TB drive with a rebuild-tree type of operation will run out of memory and fail to complete.  unRAID will run just fine otherwise.  So will the preclear of disks.  You will NOT be able to run some of the very memory hungry add-ons, nor will you even be able to install some of them.

 

As an example, any attempt to install the Java Development Environment on my 512Meg array will crash it. (Trust me... it runs out of RAM)

I have run the compiler, and even ffmpeg on 512 Meg, but again it is very easy to run out of memory if you do not assign a swap file and tune the kernel to use it.

 

All that said, if you have only 512 Meg of RAM, make sure you get a UPS so you can cleanly stop the array as any corruption of the file system is difficult to fix when the tool used to fix it crashes when it runs out of memory.  (You need to do the repair on a system with enough RAM or be able to enable a swap file and configure the kernel to use it over disk buffer allocation)

 

Joe L.