[lustre-devel] RFC: Spill device for Lustre OSD

[Andreas Dilger]

On Nov 3, 2025, at 18:58, Oleg Drokin via lustre-devel <lustre-devel at lists.lustre.org> wrote:

On Mon, 2025-11-03 at 16:33 -0800, Jinshan Xiong wrote:
I guess users won't have 1PB OSTs, will they?

There probably are already? NASA has a known 0.5P OST configuration:
https://www.nas.nasa.gov/hecc/support/kb/lustre-progressive-file-layout-(pfl)-with-ssd-and-hdd-pools_680.html#:~:text=The%20available%20SSD%20space%20in%20each%20filesystem,decimal%20(far%20right)%20labels%20of%20each%20OST

In order to maximize rebuild performance for declustered parity RAID,
there are OSTs in production with 90x20TB HDDs = 1.4 PB today,
and requests to have even larger OSTs.  We've done a bunch of work
to improve huge ldiskfs OST performance, including the hybrid OST
patches like https://review.whamcloud.com/51625 ("LU-16750 ldiskfs:
optimize metadata allocation for hybrid LUNs"), but there could still
be further improvements in supporting such large OSTs.

Cheers, Andreas
—
Andreas Dilger
Lustre Principal Architect
Whamcloud/DDN




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