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Improving ext4: bigalloc, inline data, and metadata checksumsImproving ext4: bigalloc, inline data, and metadata checksumsPosted Dec 8, 2011 17:54 UTC (Thu) by nye (guest, #51576)In reply to: Improving ext4: bigalloc, inline data, and metadata checksums by raven667 Parent article: Improving ext4: bigalloc, inline data, and metadata checksums
>Barriers are there to control the write cache after data has been posted to the storage device, to ensure that the device doesn't report completion until the data is actually perminanely committed
Surely what you're describing is a cache flush, not a barrier?
A barrier is intended to control the *order* in which two pieces of data are written, not when or even *if* they're written. A barrier *could* be implemented by issuing a cache flush in between writes (maybe this is what's commonly done in practice?) but in that case you're getting slightly more than you asked for (ie. you're getting durability of the first write), with a corresponding performance impact.
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Improving ext4: bigalloc, inline data, and metadata checksums Posted Dec 8, 2011 23:24 UTC (Thu) by raven667 (subscriber, #5198) [Link]
I think you are right, I may have misspoke.
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