I'm trying to figure out if I need a separate RAID card or if I can get the embedded one (S2600CP2 motherboard) to work fast and reliably. Without write caching (WC) enabled on a VD I'm not going to get enough performance and WC of course is not fault tolerant without a BBU or equivalent. If I upgrade (with the C600 RAID key) and enable SSD Caching, does this provide the equivalent performance to WC while at the same time providing increased fault tolerance?
In other words, does SSD Caching on a RAID1 array speed up performance while having some benefit to data protection in the case of an unexpected power loss, i.e. will I get the performance and data protection somewhat equivalent to one of the cards with included Flash and BBU (e.g. RS2VB080)?
Also, would I enable WC now on an array with SSD Caching, or never use WC?
The cache memory available on Intel® RAID controllers can improve the overall system performance. Writing data to the controller's cache memory is much faster than writing it to a storage device. Write operations appear to complete very quickly at the software application level. The Intel® RAID Controller writes the cached data to the storage device when system activity is low or when the cache is getting full. The risk of using write-back cache is that the cached data can be lost if the AC power fails before it is written to the storage device. This risk factor is eliminated when the Intel® RAID Controller has a battery back-up unit (BBU) installed.
SSD Cache uses Solid-State Devices as secondary cache and is designed to improve the read performance of the Intel RAID Controller. SSD Cache doesn't provide any data protection per sey. See the http://www.intelraid.com/files/Intel_RAID_SSD_Cache2_PB_080911.pdf SSD Cache 2.0 Feature Overview for more information.
Data Protection is another matter. As noted above, the risk of using write-back cache is that the cached data can be lost if the AC power fails before it is written to the storage device (the virtual disk). The BBU powers the cache memory for a time to allow the cached data to be written to the VD with the power gone. That's the extent of of the data protection when using write-back cache.
OK, thanks - that answers my question - i.e. the SSD Cache does not provide 1st level write-back caching, which for the motherboard I have would still be in memory and so increased chance of data loss/corruption in case of power failure.