In <4A2547B0.8020706@drobic.de>, Sandy Drobic wrote:
Lars Marowsky-Bree wrote:
On 2009-06-02T22:07:17, Zhang Weiwu
wrote: As far as I know if the hard disk of the guest os is an image file on the host OS, the host OS treats it as a file and offer to cache it in the main memory. However if vmplayer access a partition or harddisk it is not cached by the host OS's file system. That might make it even slower. Unless of course the database is in particular on a raw device that is directly accessed from the guest OS, as Sandy pointed out.
The caching doesn't make a difference, as it is not really different.
The question itself is not relevant. Fact is that performance will increase a lot if you use a raw device.
Well, then that software is written poorly. For example, the kernel can use a file or a partition/disk for swap. Both are virtually the same speed. There's few reasons accessing physical storage through a file would be any slower that accessing it through a block device. (The most noticable would be severe fragmentation, but modern filesystems don't suffer from that often.) In the rare case that the program knows how to buffer/cache the device better than the kernel, using the O_DIRECT flag when opening the file/block device will cause all reads/writes to bypass the kernels buffer/cache system. -- Boyd Stephen Smith Jr. ,= ,-_-. =. bss@iguanasuicide.net ((_/)o o(\_)) ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-' http://iguanasuicide.net/ \_/