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I’m pretty sure you can open disks raw in Linux. But then the disk is owned by the RDBMS. Ceph can do this in its BlueStore engine. But yeah, I understand you
by vlovich123 3y ago
I’m pretty sure you can open disks raw in Linux. But then the disk is owned by the RDBMS. Ceph can do this in its BlueStore engine.
But yeah, I understand you weren’t talking about buffers, I was just highlighting that O_DIRECT and raw devices are totally separate problems from having a user space cache that can be evicted by the kernel memory and reconstructed by the application lazily.
- hyc_symas 3y agoYes, you can use raw block devices in Linux. LMDB works on raw block devices as well. You get write-through cache behavior; writes are immediate but everything still goes into the page cache. I've not yet bothered to check how things work with raw devices in Windows. I believe only Admins can even operate on them so it would be kind of limited usefulness.
- vlovich123 3y agoI don’t believe the page cache is accessed if you open the raw block device via o_direct.