On 12/5/24 13:07, Michael Stone wrote: > On Thu, Dec 05, 2024 at 10:55:48AM -0500, e...@gmx.us wrote: >> How do I tell how many lanes a given drive uses (preferably before purchase)? > > It would be buried in the technical docs. I've only seen 4x drives (but I'm > sure there may be some cheaper drives with fewer). On the motherboard side > it's common to see 2 lanes in some slots for the simple reason that there > are a limited number of lanes from the CPU--most people would rather have a > slower-connected drive than none at all.
To find out if the motherboard imposed any limitations, I checked the manual. I found these tables, which I can't see the implications of: M2D_32G M.2 connector +-------------+---------+---------+---------+---------+---------+---------+ |\ Connector | SATA3_0 | SATA3_1 | SATA3_2 | SATA3_3 | SATA3_4 | SATA3_5 | + \----------\+---------+---------+---------+---------+---------+---------+ | Type of SSD | SATA_Express | SATA_Express | - | +-------------+---------+---------+---------+---------+---------+---------+ | SATA SSD | OK | OK | OK | X | OK | OK | +-------------+---------+---------+---------+---------+---------+---------+ | | OK | OK | - | +-------------+---------+---------+---------+---------+---------+---------+ | PCIe x4 SSD | X | X | X | X | OK | OK | +-------------+---------+---------+---------+---------+---------+---------+ | | OK (note) | X | - | +-------------+---------+---------+---------+---------+---------+---------+ | PCIe x2 SSD | OK | OK | X | X | OK | OK | +-------------+---------+---------+---------+---------+---------+---------+ | | OK | X | - | +-------------+---------+---------+---------+---------+---------+---------+ Note: The PCIe x4 SSD runs at x2 speed. M2A_32G M.2 connector +-------------+---------+---------+---------+---------+---------+---------+ |\ Connector | SATA3_0 | SATA3_1 | SATA3_2 | SATA3_3 | SATA3_4 | SATA3_5 | + \----------\+---------+---------+---------+---------+---------+---------+ | Type of SSD | SATA_Express | SATA_Express | - | +-------------+---------+---------+---------+---------+---------+---------+ | SATA SSD | no | OK | OK | X | OK | OK | +-------------+---------+---------+---------+---------+---------+---------+ | | OK | OK | - | +-------------+---------+---------+---------+---------+---------+---------+ | PCIe x4 SSD | OK | OK | OK | OK | OK | OK | +-------------+---------+---------+---------+---------+---------+---------+ | | OK | OK | - | +-------------+---------+---------+---------+---------+---------+---------+ | PCIe x2 SSD | OK | OK | OK | OK | OK | OK | +-------------+---------+---------+---------+---------+---------+---------+ | | OK | OK | - | +-------------+---------+---------+---------+---------+---------+---------+ Yes, the tables were in that order. Not sure why. In the book "OK" and "X" were a checkmark and a times-X respectively, but they're hard to type. In each table, the even-numbered rows were darker grey, so I guess they go together. It gets confusing when they try to re-use the table's structure for (mostly) unrelated data. I don't know why they didn't just make the tables two columns wider and half as tall. On a side note, what are SATA Express ports good for? They're narrower than standard SATA ports. Anyhow it looks like M2A_32G is more capable in general, but there are weird restrictions everywhere. Also it looks like there's a way to assign what's in the M.2 slot to another SATA port, and I need to find out how that's done, if I should acquire another M.2 drive. > E.g.: my motherboard has something like 4x v5 + 4x v4 + 2x v4 + 4x v3. Let's > say I have 2 v4 drives and 1 v3 drive. If I put one v4 drive in the 4x v5 > slot, one in the 4x v4 slot, and the v3 drive in the 4x v3 slot, all the > drives will operate at their peak efficiency. If I put a 4x v4 drive in the > 2x v4 or 4x v3 slot, it will operate at the same lower level (half the peak > bandwidth). Also, if I put the v3 drive in the 2x v4 slot it will only be > able to use half of its bandwidth, because it will only run at 2x v3 (as it > is a v3 drive). Bottom line, it's worth checking the motherboard > documentation if you have multiple M.2 slots, but only because it costs > nothing to do so. Man, I need to play with some better gear. This is almost entirely academic. >> Is one kind more long-lived than the other? > > Not due specifically to the interface. At the same price point you'll > probably have similar longevity, though sata drives are moving in the > direction of less bang for the buck because there aren't many new ones being > developed and the sales volume is going NVMe. Right, I've already had to go from 1T spinning-rust drives to 2T, not because I was running out of room, but because the selection of 1T drives was so paltry. Generally I don't mind things being slow (I'm used to dealing with slow computers), but money is in short supply and cool hardware costs money. So I'm more of a trailing-edge consumer.
