I've been doing some reading and I have a feeling that the answer is "no", but before making an implementation decision that has the potential to haunt me for years:
Can you use SSDs as pure [write] cache in Windows 2012? For example, by setting
-WriteCacheSize to the total size of the fast storage tier.
I have a reasonable amount of experience using ZFS but almost no experience with Windows storage pools, and ideally what I'm looking for from Win2012 is a cache attached to a pool, not tiered storage.
That seems to be impossible, as in a Win2012 tiered storage model a particular block of data is stored either on SSD or HDD. The SSD acts as a read cache only in the sense that frequently accessed data will be moved to the SSD tier. However the fast tier does act as a write cache.
Also, I'd need as many SSDs in the fast tier as there are HDDs in the normal tier. Is that correct? Or is it just as many SSDs as needed to achieve the same level of resiliency as the HDD tier?
Finally, I'm hoping that someone can help me understand the way the write cache is allocated across SSDs. Is the cache written across SSDs in the same resiliency mode as the volume?
My ideal configuration is something which ZFS offers: A 4x 64GB SSD mirror/stripe (~RAID10) read/write cache attached to a 8x 4TB single parity (~RAID5) pool.
Since my implementation is write-intensive, I would be OK with an SSD tier that is 100% allocated to the write cache with no SSD-backed "read cache". I believe this is achievable when setting up a volume in PS using
New-VirtualDisk [..] –WriteCacheSize xxGB and setting the write cache size to 100% of the fast tier size. But knowing Windows I have a feeling that might cause steam to come out of the server.