Improving IO with FlashCache

Posted by Devator on Server Fault See other posts from Server Fault or by Devator
Published on 2012-11-15T16:22:02Z Indexed on 2012/11/15 17:03 UTC
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kvm-virtualization

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lvm

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flashcache

I have a server with 2 HDD's (2x 1 TB), running in RAID 1 (SW-RAID). I want to improve IO performance by using flashcache. There are running KVM virtual machines on it, using LVM.

Regarding this, I have the following questions:

Will this even work? flashcache works for block devices, however these are all virtual machines with their own setup.
How much would I expect to increase performance? Most virtual machines run websites and some host games.
How big does the SSD needs to be? Would having a bigger SSD increase performance since it's able to cache more files?
What happens if the SSD dies? Would flashcache retrieve files from the traditional HDD and I could simply replace the SSD?
How much faster would writeback be in comparison with writethrough and writearound?

I have no access to a test system unfortunately, so could I install flashcache on a live server without unmounting the the disks? I found a great tutorial here which I would be using.

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