Paul Richards wrote:
2009/9/2 Paul Richards <[email protected]>:
Is there a way to combine a large slow drive with a fast small drive
in such a way that the faster drive simply becomes a cache for the
larger drive?
I imagine a computer where I'd like to have a small fast SSD and a
large but slow spinning disk. I'd like to put the two block devices
together so that I'm presented with a single logical block device,
where the operating system is using the SSD as a cache (either
inclusive or exclusive, write-though or otherwise) of the spinning
disk.
Is there some magic in LVM that can do this?
If there is nothing at the block device level can it be done at the
filesystem level?
This looks close:
http://www.cis.fiu.edu/~zhaom/dmcache
But unfortunately this isn't available in a standard Debian
installation. Perhaps I simply need to wait a while longer.
Hybrid drives were experimented with, and found not to be economically
feasible. (Windows Vista has the ReadyBoost feature.) Soon enough,
SSDs will be large enough, reliable enough, and cheap enough to be
mainstream. Until then, if speed is of the essence, buy more RAM and
fast SAS hard drives.
Mark Allums
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