snapshot performance

Hi,

I'm using LVM1 on 2.4.18 without any problem. However, after I take a snapshot of a volume, the write performance to the original volume is degraded by about 5 times. Why such a big degrade?

Moreover, I expect only the first time write should involve copying the original data block. So the later write operations into the original volume should not have performance degradation. However, this is not true. The latter writes are also very slow.

Should I upgrade to DM and LVM2? Will this improve snapshot performance?

Thanks for any help.