Dirty pages are pages of cache data that has been written by a host to array cache, but has not yet been committed to disk.  “Good” dirty pages % depends on the low/high watermarks for the most part. So if your watermarks are set to 60/80, then dirty pages between 60ish and 80ish are expected. The cache engine maintains as many dirty pages as possible within watermarks in order to increase cache hit ratios. When dirty pages climbs over the high watermark, the cache engine begins “high watermark flushing” to start moving the dirty pages out to disk. While flushing, as the dirty pages % drops down to the low watermark, flushing stops. As long as dirty pages is essentially between the two watermarks, then the system is operating normally.  If host write throughput exceeds the capability of cache to flush data to disk, then dirty pages will begin to climb over the high watermark until the problem subsides. If dirty pages hits 100%, this means that all data in cache needs to be committed to disk and there is no room in cache to accept new writes until some amount of data is flushed. This will cause “forced flushing” which will impact performance for not only the active host, but other hosts sharing the array.  I wouldn’t worry about 5% over the high watermark, but if you are seeing 99% regularly then you could be experiencing forced flushing which is bad.  Hope that helps!  Richard J Anderson
any one can explain how can understand this info, easy way. whats dirty pages %,thank you.
Analyzer cx4 - good or bad? having constant dirty pages % from 60 to 85