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Comment by lykron | Hacker News Reader

By Tiering, I'm talking about moving blocks of data from slower to faster or visa verse. If I have 10TB of 10k IOPS storage and 100TB of 1k IOPS storage in a tiered setup, data that is frequently accessed would reside in the 10k IOPS tier while less frequently accessed data would be in the 1k tier. In this case, the blocks of popular repositories would be stored in SSD, while the blocks of your side project that you haven't touched in 4 years would be on the HDD. You still have access to it, it might just take a bit longer to clone.

Ceph can probably explain it better than I can. http://docs.ceph.com/docs/jewel/rados/operations/cache-tieri...

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That is pretty awesome. Should the SSD's for the fast storage be on the OSD nodes that also have the HDD's or should it be separate OSD nodes?

That would be something I would test. I don't know Ceph, so I would be taking a shot in the dark. I would guess it would not make much of a difference as everything is block level. I, personally, would do 1x PCIe SSD for cache, 1x 2/4TB SSD, and 2x 4TB HDD for each storage node.

Edit. If Ceph is smart enough, it would be aware of the tiers present on the node, and would tier blocks on that node. So a Block on node A will stay on node A.

The fact that you're asking this question on Hacker News leaves little doubt in my mind that you and your team are not prepared for this (running bare metal).

I read the entire article, and while you talked about having a backup system (in a single server, no less!) that can restore your dataset in a reasonable amount of time, you have no capability for disaster recovery. What happens when a plumbing leak in the datacenter causes water to dump into your server racks? How long did it take you to acquire servers, build the racks and get them ready for you to host customer data? Can your business withstand that amount of downtime (days, weeks, months?) and still operate?

These questions are the ones you need to be asking.

In other words, double your budget because you'll need a DR site in another datacenter.

They don't need another datacenter. AWS has had more issues they NYI's datacenters have had in the past year. There are many companies that are based out of a single datacenter that haven't had any major issues.

Backblaze comes to mind.

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