Dell Perc RAID cards (among others) allow you to set the disk cache policy to be either on (meaning, the individual hard disks use their built-in caches) or off (meaning, the individual disk caches are disabled). In reading discussions on the net, I find conflicting information about which setting is best. Some people say to disable the disk caches because a power failure can cause corruption of data; others say you can leave the disk caches enabled if your computer is connected to an uninterruptible power supply, and that enabling the caches improves disk performance even in RAID configurations.

Is there a definitive conclusion to which way the disk caches should be set?

Note that this is not about the RAID card's cache and caching policy – this is about the disks used in the array, not the card cache or the battery backup on the card itself.

  • What you're using the storage for seems to be important to this question. What are you using it for? – Edwin Aug 6 '15 at 0:37
  • This will be a file-intensive computer, with millions of various-sized files stored on disk and various programs reading and analyzing the files. – mhucka Aug 8 '15 at 23:50

You have answered the question yourself. If you have a UPS you can leave them on, if you don't then they should be off or else you risk data loss.

On most servers in the datacenter they will generally be using OEM firmware that uses the cache in a read only mode. (The equivalent of off) Writes will be cached by the RAID card with battery backed memory.

  • 2
    Agreed. This is a calculated risk, and there is no single "right answer". Generally leaving the disk cache disabled is considered best practice, as you still have the hardware RAID card's onboard cache to cover that functionality and most cards have battery-backed cache. – JimNim Aug 6 '15 at 15:48

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