Re: questions about SSDs and IBM i

Hello Mark,

Am 07.07.2025 um 17:55 schrieb Mark Waterbury <mark.s.waterbury@xxxxxxxxxxxxx>:

Do you think it is better to use mirrored pairs, versus RAID? I have heard and read opinions that RAID-5 or RAID-6 may "ruin" the "wear leveling" of SSDs. Is that just rumor or speculation?

As others, I have no definitive answer for you regarding IBM i.

On Linux, mdadm based software-RAID allows you to pass-through TRIM requests from the upper layers down to the device. And why not? It's a mere calculation which device to send the request to discard a block to. I'd say RAID-5 vs. SSDs allegations of "ruins wear leveling" — as a generic advice — is either hearsay, or very OS specific. Or just outdated information.

Or, perhaps just use mirrored pairs with SSDs?

If you can afford the higher loss in available space. Same as with normal disks.

Any opinions or advice in this regard?

Allow me to ask back: How much do you trust IBM to "do the right thing"? :-) In other words, if DST allows you to start parity checking over SSDs, I'd say, it's okay. But if TRIMs are really sent for deleted objects for whatever SSD configuration — or not — is something only IBM can answer definitively.

:wq! PoC