iSCSI write cache

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iSCSI write cache

Is there a way to setup on a Linux iSCSI initiator a local disk partition for write cache ?

The data would be first written on some high performance local disk and then in a second time on capacitive disks mounted through iSCSI.


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    • so are you asking for a 3 tiers vs the normal 2 tiers (not counting the local hd cache) of caching as in the system os will cache disk io then you want something like a layer of ssd then a final write to spinning disks? Or should you just buy more ram so the os can cache more disk io?
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    • The use case is to write a lot of data faster than the 1Gb ethernet link is able to transfer to the disks enclosure. The hardware cache is on the enclosure side (so after the ethernet bottleneck). So the idea is indeed emulating an SSD layer.
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    • Beware, a writeback cache does NOT mean more throughput in many situations. It must be flushed regularly. This flush has to happen over the ethernet link, so you will still be limited to your link speed during sequential write. If you are making many small changes sporadically, a writeback cache will perform beautifully. However, it will be nearly useless in a sequential write pattern or heavy continuous random writes, such as a backup, media, or highly active database server. The same is true of a read cache in most situations.

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