A post for postings sake

[SaFeHeX]

Well, as the title says i figured i would post something because nothing much has been posted in a while, or at least that i can reply to, with something usefull. So this one's a little different.

I thought i would mention one of my new arrivals in my ever growing Snap Server farm!

I haven't done much with it yet but i have recently taken delivery of a used N2000 model. It was quite expensive compared to many of my other Snaps, but it was still relatively cheap for what it is and was quite the bargain.

The N2000 is a 12 drive bay SATA/SAS unit and appears like many of the other later Snap units to be based around an OEM SuperMicro Chasis and components.

It's running GOS 6.5.023 and from what i can tell it appears to be installed on/booted from and internal SATA DOM (Disk on Module) Flash drive rather than installed on the HDD's. At the moment this is just a guess but without the DOM installed it doesn't boot. If the DOM is installed but the HDD's are removed, it boots to a recovery console that complains of not being able to find any HDD's. I have not been brave enough to zero fill the HDD's to find out the consequences but i may in the future try some 'other' blank hard drives to see how it reacts.

I also have some concerns that if the DOM ever fails i could be up the creek without a paddle, but for now at least, it all appears to work fine in it's current configuration. (With the exception of one intermittant PSU)

It's early days yet and these are just some early observations, so i figured as nothing much has been posted in a while, i'll have a ramble with some probably useless information for anyone who is bored enough to read it.

Oh, one thing i did find very odd. It arrived with 2Gb of RAM installed but according to the data sheets for the N2000 it is expandable to 4Gb. Well that's easily sorted i think to myself and set about upgrading it to the full 4Gb. I checked EVERY specification on the 2Gb stick that was fitted, exact part numbers, the lot. I checked the compatibility lists for the SuperMicro motherboard that is fitted and sure enough the exact part number for the exiting RAM was on there and i did a whole load of other checking and double checking to check i could obtain the exact and identical RAM for compatibility. Literally right down to the individual IC numbers.

After all of the above i managed to procure two additional 2Gb sticks of RAM identical in every way exept for the date/batch codes on the individual IC's fitted to the stick. I only needed the one but they were being sold as a pair and the price was right.

So i set about doing the upgrade, as easy as slicing cake you would think but sadly it wasn't so. Bear in mind i have countless years of experience with computer hardware and i had been maticulous in ensuring compatibility. So i boot up with my new 4Gb of RAM and head over to the GOS status page to check all is ok and reporting correctly and Oh no, why do i only see 3072Mb?

Ok, so i think to myself i must have done something wrong or i have a faulty stick or something, so i shut down and investigate. Consulting all the data sheets again and the official documentation on how to install RAM into an N2000 including the manual for the SM mother board it's self. Nope, i've deffinitely done it right.

I check each individual stick in place of the original stick, boot up fine and see the full 2Gb for each stick. They all work as individuals and in any combination in any of the six slots but will not work together in any way or combination to report back in GOS anything other than 3072Mb. At one point i had all 3 sticks installed and still get the same result.

I did read in the original SuperM motherboard manual that some OS's will not see anything above 3Gb and i'm not quite sure exactly why that is in this case when the overland data says the N2000 is expandable to 4Gb.

I do understand that the likes of Windows XP will only see 3Gb in a PC but i am/was surprised that GOS only appears to register 3Gb also.

At the moment i'm running back on the single, original 2Gb stick, just because i got fed up messing about with it and all the combinations i tried, so we're back to original factory spec as a just in case thing, for the time being at least.

It's a little annoying when the Motherboard it's self is capable of supporting 2x Intel quad cores and a total of 12 sticks of RAM (6 per CPU) and something like 192Gb of RAM in total if both CPU's were fitted.

The machine seems to be way more than what GOS is designed to handle and in some ways GOS is almost wasted on it. Don't get me wrong i've been a fan of Snaps for a good few years and this thing is a beast. I'm pleased with it, but just a little bit disappointed by what appears to be limitations with GOS. Maybe i could understand it better if i was running an older GOS revision but this is 6.5.023. Ok, so it's not the very latest 7.2.xxx or whatever but 6.5.023 is still only a couple of years old. The N2000 it's self was only manufactured something like 3 years ago.

Well, there's my little rambling for the day should any one be in the least bit interested.

If you have any questions fire away but i probably can't answer any more than i've mentioned. It's quite new to me but still a nice peice of kit all the same.

[Terry Kennedy]

Originally Posted by SaFeHeX

I did read in the original SuperM motherboard manual that some OS's will not see anything above 3Gb and i'm not quite sure exactly why that is in this case when the overland data says the N2000 is expandable to 4Gb.

I do understand that the likes of Windows XP will only see 3Gb in a PC but i am/was surprised that GOS only appears to register 3Gb also.

At the moment i'm running back on the single, original 2Gb stick, just because i got fed up messing about with it and all the combinations i tried, so we're back to original factory spec as a just in case thing, for the time being at least.

It's a little annoying when the Motherboard it's self is capable of supporting 2x Intel quad cores and a total of 12 sticks of RAM (6 per CPU) and something like 192Gb of RAM in total if both CPU's were fitted.

The 3GB issue isn't an operating system problem, it's a design "feature" in the original PC spec. Just like you couldn't have more than 640KB in the original PC, despite it being able to address 1MB, the space above 3GB has a buch of reserved chunks for memory-mapped devices.

In order to use more than 3GB, you need either a 64-bit operating system (and, of course, 64-bit capable CPU(s)) or a 32-bit one with PAE support (which is a bit of a hack, and not all device drivers work properly in a PAE environment). I'd bet that GOS is neither.

It's a little annoying when the Motherboard it's self is capable of supporting 2x Intel quad cores and a total of 12 sticks of RAM (6 per CPU) and something like 192Gb of RAM in total if both CPU's were fitted.

The machine seems to be way more than what GOS is designed to handle and in some ways GOS is almost wasted on it. Don't get me wrong i've been a fan of Snaps for a good few years and this thing is a beast. I'm pleased with it, but just a little bit disappointed by what appears to be limitations with GOS. Maybe i could understand it better if i was running an older GOS revision but this is 6.5.023. Ok, so it's not the very latest 7.2.xxx or whatever but 6.5.023 is still only a couple of years old. The N2000 it's self was only manufactured something like 3 years ago.

Well, if the hardware is standard you could always run some other operating system on it. If the GOS is stored on a special flash module, you could just remove that in case you ever wanted to switch back. Personally, I'm using FreeBSD + ZFS on my 32TB RAIDzilla II's.

[SaFeHeX]

Originally Posted by Terry Kennedy

The 3GB issue isn't an operating system problem, it's a design "feature" in the original PC spec. Just like you couldn't have more than 640KB in the original PC, despite it being able to address 1MB, the space above 3GB has a buch of reserved chunks for memory-mapped devices.

Ah yes, of course. I hadn't considered that some areas are reserved and mapped into the available address space. I do understand, i just hadn't put much thought into it at the time. Reading the docs and seeing "N2000 can be expanded to 4GB" was bugging me that 'they' were advertising this but then limitations that can't be easily avoided were not allowing it to be possible. Almost bordering on false advertising to the layman i guess. Thanks for reminding me and clarifying that, Terry.

Originally Posted by Terry Kennedy

Well, if the hardware is standard you could always run some other operating system on it. If the GOS is stored on a special flash module, you could just remove that in case you ever wanted to switch back. Personally, I'm using FreeBSD + ZFS on my 32TB RAIDzilla II's.

Although i say standard, it looks to be mostly SuperMicro built other than the mother board model number has a slightly different extension added to signify a modified OEM version of the original. Some components have been removed, (VGA, keyboard and mouse ports removed, for example) and some of the other unused bits in this application.

Yeah, i could run a different OS i guess but i'm quite happy for now at least, to run it as intended with GOS. I would imagine they have built in an EEPROM or similar to store the serial and server number and i have an element of fear that some other OS might overwrite or corrupt this info and render it useless for restoring to original. For now atleast the N2000 is too nice (and expensive) to risk i guess.

Your Zilla setup sounds awesome, and is certainly something to envy. I've just looked at the link and it looks even more impressive than i had first imagined. I may at some point look into some alternatives to GOS and Snaps but probably using either older servers that i have that aren't being used for anything right now or maybe a custom job in the future. I can say this though it's highly probable to be no where near as impressive as your Zilla II's. Fantastic!

Thanks for your feedback and input Terry. I do appreciate it.

[Trod]

This is actually a well known issue. Intel CPU do not support 4GB of memory on a 32-bit OS. You'll see this issue in Windows and most Linux implementations.

It IS possible to hack a patch to address it - but it can cause some instability.

AMD CPU do not suffer from this issue. If you have a Snap Server 500/600 series (All using AMD Opteron CPU) they can allocate all 4GB of memory.

The N2000 was a bridge platform and, you're correct, it's a bit more hardware than GOS was able to fully utilize at the time of release. Initially they were released with 2GB of RAM and had no 'official' upgrade path. Later revisions shipped with 4GB of RAM.

Initially Overland was going to allow the N2000 to run GOS 7.x but decided to go in a new direction with a unified platform refresh (DX Series) and as part of that effort the N2000 went into limbo. It could in theory support GOS 7.X (64-bit OS) and address a lot more memory, and even another CPU - but it would require some under-the-hood shuffling to defeat the OS 'trusted-platform' protection that is built in. This is also what prevents you from installing GOS on any regular server (along with the lack of drivers).

[Terry Kennedy]

Originally Posted by Trod

This is actually a well known issue. Intel CPU do not support 4GB of memory on a 32-bit OS. You'll see this issue in Windows and most Linux implementations.

It IS possible to hack a patch to address it - but it can cause some instability.

AMD CPU do not suffer from this issue. If you have a Snap Server 500/600 series (All using AMD Opteron CPU) they can allocate all 4GB of memory.

The AMD Opteron was the first 64-bit x86-family CPU. As opposed to other 64-bit CPUs which preceded it, including Itanium which had such a laughably slow x86 hardware mode that a "hail mary" software emulator outperformed it by around 10-to-1.

Older (32-bit) Intel CPUs can address more than 4 GB of memory (which can also involve moving some or all of the unavailable RAM between 3.5GB and 4GB above the 4GB line, if the chipset supports it). There are driver issues when trying to access memory above 4GB in PAE mode - many non-PAE-aware drivers will simply transfer from / to the wrong address in memory.

There aren't that many x86 systems that come with huge amounts of memory but not 64-bit CPUs. As a result, PAE (even if supported by all needed drivers) is generally not a "win". For example, the Tyan S2721-533 motherboard with 4GB of RAM installed (Socket 604 Xeon CPUs) will give you a whopping 128MB "above the line" in PAE mode.

[Trod]

Ahh No - Opteron was not the first 64-bit CPU. It was arguably the first widely available 64-bit CPU (price wise) but it is handily pre-dated by Intel's Itanium (IA64), Sparc 64, DEC Alpha and plenty of mini and supercomputers going back to the mid 80's.

This being said, you are absolutely correct about PAE. It is worthless because of the reserved memory spaces required for addressing things like video memory or shadowing BIOS use so much of the high memory area that it doesn't make any significant difference.

Either way the bottom line is that a 64-Bit Intel CPU (consumer or server) won't show more than 3.5Gb of memory on a 32-bit OS without ill-advised tweaking of the kernel memory maps.