Hard Disk Cache

[George Luiz]

Hi,

Probably this is a stupid question, but I have to ask :)

When I read a hard disk specification there is *cache* size field. This cache at the HARD DISK is used only for reading, right? I wonder if it could be used for write caching a power loss could corrupt data and as far as I know hard disks does not have a battery, only disk controllers.

This way I conclude that I can enable write caching only at the controller level because this can be battery backed and the cache field at hard disk specifications is for reading only.

Am I correct?

Thanks!

[Uwe Zessin]

On some arrays it is possible to turn on write-back caching at the disk drive level, but as you correctly said "disk drives do not have a battery". It is turned off by default because the vendor cannot make sure a customer's array is always running on a redundant or reliable power source (even UPSes can fail!).