On Sat, 24 Oct 2009, Bob Friesenhahn wrote:

Is solaris incapable of issuing a SATA command FLUSH CACHE EXT?

It issues one for each update to the intent log.

I should mention that FLASH SSDs without a capacitor/battery-backed cache flush (like the X25-E) are likely to get burned out pretty quickly if they respect each cache flush request. The reason is that each write needs to update a full FLASH metablock. This means that a small 4K syncronous update forces a write of a full FLASH metablock in the X25-E. I don't know the size of the FLASH metablock in the X25-E (seems to be a closely-held secret), but perhaps it is 128K, 256K, or 512K.

The rumor that disabling the "cache" on the X25-E disables the wear leveling is probably incorrect. It is much more likely that disabling the "cache" causes each write to erase and write a full FLASH metablock (known as "write amplification"), therefore causing the device to wear out much more quickly than if it deferred writes.


Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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