Underorivisioning is the basic idea of not allocating the full physical disk space. I first learned about it in building disgusting iops database arrays for customers. The concept there is to only provision a certain percentage of the physical disk in order to take advantage of aural density performance boost. (unsure if my spelling here). 

In the SSD world it means the same thing, but instead of a performance boost it is to sacrifice disk space to grant a larger area for wear leveling. This also allows you to look into the drives that perform faster with more physical chips and instead of wasted space it gains a new purpose. Especially if you are using ssds for storage tiring or some level of disk/system cache. 


On Fri, Oct 15, 2021, 9:53 PM Michael Butash <michael@butash.net> wrote:
Underprovisioning?  Maybe a new concept for me, not dealt with this - do tell.

Most times I do my normal mdraid(1)/luks/lvm/ext4 stack atop flash disks, and with samsungs not lost a disk, but otherwise blew up crucial, adata, and at least one more I've forgotten along the way.  I still don't run or use trim to this day, and not really felt pain for it with samsung.  My current full-time desktop isn't raid1 with only a toshiba m.2 1tb flash disk in it, and after 5 or so years can't complain it's still kicking...  Even with just luks/lvm (no mdraid) and no trim, it hasn't killed it, so hoping they adopted like tech to Samsung to stave off the suck.

I got a few samsung 980pro m.2's for my desktop to rebuild, and as soon as I care enough to figure out zfs encryption and booting on that thing I'll probably switch back to it.  The two prior 860pro's are still solid in that thing though using it more as a server than a desktop for heavy virtualization.

-mb


On Fri, Oct 15, 2021 at 9:26 PM Stephen Partington via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
If you are using SSD's in raid i would suggest underprovisioning. Unless you raid card or raid software supports trim. even still it is a good idea to extend drive life.

On Fri, Oct 15, 2021 at 9:23 PM Michael Butash via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
Can be done?  Sure.  Should be done?  Maybe...

I've used ssd's since they've been around, super speed boost for any desktop really, but I'd run them typically in raid1, and for the first few years they'd reliably die, one disk or another around the 6mo mark.  I didn't do trim, as it defeats luks encryption, and often simply doesn't work otherwise with various filesystem layers (mdraid, luks, zfs, etc), and well yeah, they all died horrible deaths.  Not since Samsung introduced wear-leveling in their SSD architectures did the problem mostly go away, and I've begun to use Samsung SSD/M.2 (even sd cards) exclusively for this, and have not lost a disk since.

Not sure how commonly this is used in other vendors, but something if ever doing raid or other enterprise-y functions, something to look for.

-mb


On Fri, Oct 15, 2021 at 10:23 AM Michael via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
Can raid5 be done on ssd?

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