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I'm setting up a server with and SSD as the primary drive, and would like to duplicate the data onto a cheaper drive as a block-level backup (à la RAID1).

Since I don't want to hobble the performance of the SSD I was considering setting up DRBD with asynchronous mirroring so that changes get queued up for the spindle drive and eventually synced up once IO permits.

But I'd like to know if anyone has tries something like this and if there are any "gotchas" to pay attention to. Alternately, if there's a better technology to solve the same problem, please share.

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This should work, but I'd like to remind you that the only time you'll see a massive performance improvement over regular drives with an SSD is on random reads, which spindle drives aren't good at. If your workload does 70% reads (like most tend to), even synchronous wouldn't be that bad.

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He could see a performance hit on random/sequential writes with a fully synchronous setup. SSDs are just absolutely crushing spindled drives in every category including write performance. The only 2 categories HDDs have over SSDs are still price and reliability. – bot403 Apr 17 '12 at 15:49

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