Tuesday spent “tinkering”

Yesterday I decided it was time to work out exactly what is going on with my home server. This was one of those little jobs that I’d decided wouldn’t require much physical effort, and that could be picked up and put down again as required when I felt tired. In short, ideal for my current situation.

The main problem is that I have three large SATA drives in the server, that I want to run as a RAID 5 array, but the motherboard I am using (in common with almost all other mini-itx motherboards) only supports two SATA drives. Originally I tried to work around this by using a PATA to SATA converter, but found that it resulted in some odd errors and what appeared to be data loss. So I bought a PCI card with a pair of SATA ports, based around the SiL3124 chipset, to provide me with support for a total of four SATA drives. However, any drive connected to that PCI card started showing errors whenever the I/O rate went above some arbitrary level, making it completely unsuitable for inclusion in a RAID array.

So yesterday I replaced the SiL3124 PCI card with another based on the VIA VT6421, which provides 3 x SATA ports and an IDE port, and since I had the server in pieces, took the opportunity to add an IDE to Compact Flash adapter, along with an 8GB Compact Flash card.

My intention was to be able to install the operating system onto the Compact Flash card, and then use the 3 x SATA drives purely as a RAID 5 array for data storage. By installing the operating system onto the memory card (with no moving parts that wear out) I would minimise the chance of any failures, making the system more reliable. The RAID 5 array would provide redundancy for my data storage, allowing a drive to fail without impacting my data.

However, in the tradition of plans laid by mice and men, when I got everything updated, the drive connected to the new PCI card still exhibits strange I/O errors. And swapping the drives around still leads to errors only from the drive connected to the PCI card. Which leaves me with the frustrating conclusion that it’s probably something to do with the implementation of the PCI bus on the motherboard – which is not what I was hoping for.

This somewhat Frankensteinian server has worked well for the last couple of years, but I’m starting to think that given how much of my home now depends on it working smoothly, it may be sensible to actually buy a new server designed specifically for the task, rather than wasting precious time chasing down obscure hardware issues in my DIY creation. At the moment, this one looks just about perfect (apart from the price … gulp …) would allow me to reuse my existing drives, and can probably even be made to boot from my compact flash card still. Decisions, decisions!

Update: I upgraded to Jaunty (9.04) recently, and the problem with PCI-based SATA cards has magically fixed itself. So it looks like this really was a problem with the way the Linux kernel and it’s SATA drivers were interacting with the hardware, rather than the hardware itself. Now I just need to find the time to take the server down, and grow the RAID1 array into a RAID5 array. It’s back on the todo list, albeit as a low-priority item.

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