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http://www.adaptec.com/en-us/_common/maxcache/

http://www.adaptec.com/en-us/_common/hybrid-raid/

They sound similar, but there's no detailed description of how either of them work.

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Ah - there is. Seriously. There are some white papers. Maybe you should not expect them to be ll in one place? –  TomTom Oct 12 '11 at 10:34

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Obviously MaxCache is using an SSD pool as a large read cache for "hot data", while HybridRAID is the implementation of a read bias towards SSD disks in setups where you have a RAID 1 setup with one SSD and one HDD.

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Exactly. Also in a 20 disc hybrid raid, you need Raid 10 and half the discs being SSD - maxcache is a front end cache in front of the discs for the often requested data ONLY. –  TomTom Oct 12 '11 at 10:34
    
Come to think of it, HybridRAID sounds like an incredibly stupid idea. For any reasonably sized storage system, you would spend more money than for a tiered storage solution with none of the advantages. –  the-wabbit Oct 12 '11 at 13:01
    
Ah - yes. Except for example a read heavy database where you SAVE money. With limited writes the write budget may be ok for the normal disc - and you get the extreme IOPS and latency for read access. Note: The wolls is more comlpex than your simple mind. The database server I use right now has nearly 1000gb SSD secnod level cache in front of the discs. We would love a full hybrid raid approach. No way to tier that stuff either. –  TomTom Oct 12 '11 at 13:27
    
Writes still would need to be performed synchronously. Unless you have a database with virtually no disk writes (at least compared to your write cache size), they are likely to kill the array's overall performance anyway. This is not just "read-heavy" but a border case for OLAP-only style of databases - which in turn would have other optimization techniques working out more effectively than throwing SSDs at them (admittedly this is much easier for engineering and DBAs). –  the-wabbit Oct 12 '11 at 13:40
    
Ah, no. Out of experience. Writes would not kill the perforamcne as all reads go to the ssd only. Look at Oracle ExaData for something that has heavy ssd caches. –  TomTom Oct 12 '11 at 14:20

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