Netgear ReadyNAS RN526X Hardware

In a previous blog post I mentioned that I have a Netgear ReadyNAS RN526X, as wel as the fact that Netgear is killing off the ReadyNAS product. I also mentioned I wasn’t ready to retire my NAS box and I’m concerned Netgear will stop updating the software, which already runs on a very old base OS, Debian Jessie. I will be exploring if it’s possible to replace the OS with something else. There are multiple options, both Open Source and commercial, that I’m willing to consider. First, though, I need to understand the hardware.

The 526X is an x86 based NAS, as opposed to the low end of the lineup which ran various iterations of ARM processors. Mine came with 4 GB of RAM. Being a dual core Pentium D processor with 4 GB of RAM, it’s not going to be a performance powerhouse, which might present some limitations. I think the CPU might be fine, but what about the RAM?


The machine comes with 4 GB of RAM, and I believe there was a version of it that you could buy at retail with 8 GB. This gives a clue that it might be upgradeable.

As it turns out, it has 4 DIMM slots, and the 4 GB variant comes with 1 slot occupied with a 4 GB module. I found a picture online of an 8 GB variant with 2 slots occupied with the same module I found in mine. I also found a posting from what might have been a Netgear employee stating it can support up to 64 GB of RAM, so not only are there 4 slots, they appear to all be wired up. Score!

This is important to note because platforms like Unraid and TrueNAS recommend at least 8 GB of RAM. Since it’s upgradeable, this is the first thing I really want to do. Besides, it should also help with performance as I figure other things out.

So what kind of RAM is it? I was worried it might have some old hardware. I didn’t think it’d be as old as DDR2, but DDR3 might be hard to get and expensive. The module installed is DDR4. Once again, Score! But wait…it’s ECC RAM.

ECC stands for error correction code. This requires extra hardware on the module and support by the underlying platform. The problem is, if it’s wired up for ECC RAM, it cannot take standard memory. I have to get ECC RAM as an upgrade. I also noted that the module installed is single rank. I’ve run into problems with higher ranked modules in older systems. Generally, this shouldn’t matter though. I searched around to see if anyone else did this upgrade and one poster posted the exact memory he used in his upgrade, which was dual ranked memory. Good, this should make the search easier.

One of the problems with buying ECC memory is it tends to be more expensive than standard memory. I found a 32 GB kit in 2 16 GB modules, which appears to be the maximum module size supported by this platform, so they should work and I increase the RAM eight-fold.

This upgrade is happening now.

Root Storage

I’ve found that there is some kind of firmware on this system. The base OS does get installed on the hard drives in the system, but it seems to originate from within. I could install fresh new drives, boot it up, and there’s a clean system in there running without downloading anything.

This hints at some internal storage, but it doesn’t appear to the OS. I can only guess that there is some pre-boot environment that assembles the software raid and then locates the OS stored within.

I was able to locate a weird daughter board near the USB ports on the mainboard labeled USB-daughter-board. The chip on the underside looked like a flash chip. The chip on the top might be a USB flash controller. Let’s look it up.

The top chip is a Phison PS2251-03. A DDG search turns up this page , which tells me it’s a USB 2.0 flash controller supporting up to 64 GB of storage and some pretty garbage speed.

The chip on the underside appears to be a Toshiba 2 GB SLC flash chip.

So this module is a 2 GB USB connected flash chip.

For now, I’m just researching the hardware, so we’ll figure out how this is all connected later.


If you look up pictures of the RN526X, you’ll find there’s no outputs on it at all. No VGA, DVI, HDMI, or even serial. It only offers connectivity.

There’s a spot on the back that says UART, but there’s no connectivity there. My suspicion is there is a UART header on the mainboard somewhere. I took some pictures of unused header pins to do further research into if they might align with a wireable UART. If so, I might have a built-in serial interface to use.

Alternatively, there appears to be a PCIe slot, as well as a low profile slot in the back. There’s not a lot of space inside, but it looks like a simple low profile serial interface card should fit with a PCIe extension as the slot in the back is at a right angle to the mainboard.

Again, I’m just looking at the hardware, so we’ll figure out interfacing later.


I’m noting this one close to the end, for now, because it might be the least important aspect of this thing. It’s an x86_64 CPU. It has 2 cores and hyperthreading, so 4 total logical cores. It has a base clock of 2.2 GHz and can boost to 2.6 GHz. I’m not sure if Netgear leaves TurboBoost enabled, but honestly, I don’t really care. It just needs to handle being a NAS. PassMark score seems to indicate it performs about like a 3rd generation mobile Core i7, though.

Being a 64 bit x86 CPU, though, means I basically have the world of available NAS software platforms available to me.

Drive Bays

The RN526X is a 2nd generation 5 class 6 bay NAS. The chassis is designed to make the drives hot swappable, and I’ve had the opportunity to test this. I went into this chassis with 4 2 TB drives from my old RN104. Later, I upgraded these to 3 TB drives, which the ReadyNAS OS handled beautifully. The process was fully automatic provided I was patient swapping one drive at a time and waiting for resync. Later, I added 2 more 3 TB drives. Later, still, I had a drive failure, and the process of replacing it was easy. Everything was done online. So…hot swap is good.

The drive trays are tool-free. However, they are 3.5" drive trays. Looking at the trays, though, they might accommodate 2.5" drives, which is something that I desire for the future, as, eventually, I want to migrate to SSD. I have old SATA SSDs I can test fit while powered off to confirm the fit and alignment of the IO port.

If this chassis does, in fact, accommodate 2.5" drives, and I’m able to load my own NAS OS to replace ReadyNAS OS, I can’t see a reason why this machine couldn’t last me another 5+ years.