This may sound like an odd question, but it's generated some spirited discussion with some of my colleagues. Consider a moderately sized RAID array consisting of something like eight or twelve disks. When buying the initial batch of disks, or buying replacements to enlarge the array or refresh the hardware, there are two broad approaches one could take:

Buy all the drives in one order from one vendor, and receive one large box containing all the disks. Order one disk apiece from a variety of vendors, and/or spread out (over a period of days or weeks) several orders of one disk apiece.

There's some middle ground, obviously, but these are the main opposing mindsets. I've been genuinely curious which approach is more sensible in terms of reducing the risk of catastrophic failure of the array. (Let's define that as "25% of the disks fail within a time window equal to how long it takes to resilver the array once.") The logic being, if all the disks came from the same place, they might all have the same underlying defects waiting to strike. The same timebomb with the same initial countdown on the clock, if you will.

I've collected a couple of the more common pros and cons for each approach, but some of them feel like conjecture and gut instinct instead of hard evidence-based data.

Buy all at once, pros

Less time spent in research/ordering phase.

Minimizes shipping cost if the vendor charges for it.

Disks are pretty much guaranteed to have the same firmware version and the same "quirks" in their operational characteristics (temperature, vibration, etc.)

Price increases/stock shortages unlikely stall the project midway.

Each next disk is on-hand the moment it's required to be installed.

Serial numbers are all known upfront, disks can be installed in the enclosure in order of increasing serial number. Seems overly fussy, but some folks seem to value that. (I guess their management interface sorts the disks by serial number instead of hardware port order...?)

Buy all at once, cons

All disks (probably) came from the same factory, made at the same time, of the same materials. They were stored in the same environment, and subject to the same potential abuses during transit. Any defect or damage present in one is likely present in all.

If the drives are being replaced one-at-a-time into an existing array and each new disk needs to be resilvered individually, it could be potentially weeks before the last disk from the order is installed and discovered to be faulty. The return/replacement window with the vendor may expire during this time.

Can't take advantage of near-future price decreases that may occur during the project.

Buy individually, pros

If one disk fails, it shares very little manufacturing/transit history with any of the other disks. If the failure was caused by something in manufacturing or transit, the root cause likely did not occur in any other disk.

If a disk is dead on arrival or fails during the first hours of use, that will be detected shortly after the shipment arrives and the return process may go more smoothly.

Buy individually, cons

Takes a significant amount of time to find enough vendors with agreeable prices. Order tracking, delivery failure, damaged item returns, and other issues can be time-consuming to resolve.

Potentially higher shipping costs.

A very real possibility exists that a new disk will be required but none will be on-hand, stalling the project.

Imagined benefit. Regardless of the vendor or date purchased, all the disks came from the same place and are really the same. Manufacturing defects would have been detected by quality control and substandard disks would not have been sold. Shipping damage would have to be so egregious (and plainly visible to the naked eye) that damaged drives would be obvious upon unpacking.

If we're going simply by bullet point count, "buy in bulk" wins pretty clearly. But some of the pros are weak, and some of the cons are strong. Many of the bullet points simply state the logical inverse of some of the others. Some of these things may be absurd superstition. But if superstition does a better job at maintaining array integrity, I guess I'd be willing to go along with it.

Which group is most sensible here?

UPDATE: I have data relevant to this discussion. The last array I personally built (about four years ago) had eight disks. I ordered from one single vendor, but split the purchase into two orders of four disks each, about one month apart. One disk of the array failed within the first hours of running. It was from the first batch, and the return window for that order had closed in the time it took to spin everything up.

Four years later, the seven original disks plus one replacement are still running error-free. (knock on wood.)