RAID at home

Sun, 2011-08-21 09:18 by admin · Forum/category:

This is a report of some experience with RAID 5 in the home.

We started out here with a HighPoint RocketRAID 2300 controller that does part of its work in hardware, but relies for another large part of its duty on an elaborate driver.

The idea is fine and should work much like a pure hardware RAID controller, if only it had the same quality. But there are some obvious problems, like:

  • This kind of controller is not used much in the professional area and therefore gets less scrutiny and testing.
  • Each operating system needs its own driver, so the installation count for each driver is lower. Consequently again each one gets less scrutiny and testing.

Nonetheless, after overcoming initial difficulties and living with the occasional non-recognition by the BIOS, the controller did its work, and the performance was excellent, as hoped.

However, recently we went through some disk reconfiguration procedures, straightforward operations like modifying partitions, adding a disk, etc., and then it happened. The controller ran wild for a few nasty seconds and destroyed everything in its reach. We still have to test some disks for lasting damage.

But this was a one-time occurrence, and we have no clue why it happened and how often something like this happens. Still, like a burnt child, we would not touch any controller from that company with a 10 foot pole again for now.

So we went upmarket with an Adaptec ASR-6805/SGL 8 port internal hardware RAID controller, which by itself costs as much as a whole computer.

The first experience was horrible, as the controller did not recognize a single disk. We could trace this back to the 4-fold fan-out SDS cables, which were wrongly wired. They came from a different manufacturer, www.digitus-professional.com. Not so professional, it seems.

After installing new cables, the controller recognized and used three of the five connected hard disks. Its manual has a list of compatible hard disks, which is only a small subset of all available hard disks. It may or may not recognize disks that are not on the list.

This is stupid for a home environment, where you often already have some disks and don't want to throw them away. It shows one of the differences between a home environment and a company environment, where this kind of controller is mostly used.

So we are now running it with these three disks and will buy new ones. Even so it suddenly rejected one of the disks and demanded to rebuild the array. The good side is that (a) the rebuilding went smoothly and without data loss, and (b) the array seems to be stable since then.

My conclusion is that the RAID route is problematic and that you run a certain risk of running into difficult problems. The reasons may be that RAID is a small proportion of the market, so things are expensive and not mainstream, with all attendant consequences.

RAID controllers are mainstream in heavyweight servers, but these are typically run by companies with a bunch of administrators and a support contract, a totally different situation, compared to a home computing environment, time- and money-wise.

Of course you always have a fair chance that you build your RAID and have no problems at all. But you have to reckon with the risk.

My personal stance is that I would not use RAID unless I had very good reasons and were almost forced to go that way. Or if I just wanted to experiment with it to gather experience.

An interesting alternative nowadays is SSD for the operating system, programs, and heavily used data, plus a large conventional disk, like 2 TB or more, for the rest, typically media files that don't need speed, and for a primary daily backup.

However, SSD is again a problematic technology, and there are incredibly poor Solid State Disks on the market. Be wary and buy OCZ Vertex or Intel or whatever the latest thorough tests point to.

A good SSD can beat RAID 5 with a few disks.

Of course hardly anything can beat a RAID consisting of SSD (a RAED :-).

RAID = Redundant Array of Inexpensive Disks