On Mon, Jan 12, 2004 at 08:23:33PM +0000, Nick Hill wrote:
This would be cured by moving the database to solid state memory. Mechanical media has a very long seek time and when many seeks are required, become unreliable.
Either: Run two MySQL instances, one starting after the finest grained database files have been copied to ramdisk. Replicate database to a hard disk file.
Or Install a solid state IDE disk. For example, a 4Gb Compact Flash card has an IDE interface built in as part of the specifications. Access time 0.1ms comapred to mechanical 8.5ms. 85x faster. CF to IDE cables are trivial and available.
To put it another way, you would need 85 mechanical drives to provide the seek performance of a solid state equivalent.
Uh, except for that wondrous innovation known as caching...
Ramdisks have no place beyond MS/PC-DOS, Knoppix, and OS install floppies. Why dedicate a gob of memory to a ram disk when you can achieve similar performance with the OS's caching facility while also allowing that memory to be conscripted for other uses should the need arise?
Flash devices have rather serious write-cycle limitations. As mysql does not do anything to avoid hot spots, such a setup would likely not last long.
As to the Apple RAID boxes, my investigations a while back indicated that they are not really redundant. Each box is two seperate RAID devices. So you have to do software raid between them if you want to avoid a single point of failure. This may or may not be a problem, but is not explicitly mentioned in the apple literature. I'm not sure this is a deal breaker, but it is certainly something to think about.