ZIP and LZW won't harm the image in any way - just as good as uncompressed except for possible support issues in non-Adobe software. Compressing generally requires more processing than decompressing - LZW or ZIP shouldn't slow down a read too much, but the initial save will probably take longer. As Andy mentioned, compressed images can often be read faster than uncompressed images, especially if you have a fast processor and the compression ratio is high.
In my experience, ZIP has always been smaller than LZW for all types of images. Saving RGB, CMYK, Lab and multi-channel images with per-channel order instead of interleaved will increase the compression ratio (often significantly) because there is stronger correlation between the pixel values within one channel than between the channels.
A RAID5 array, 2 disk RAID1, or manual mirroring of 2 drives often provides a stronger sense of security than it deserves. Consider that when one disk fails, the whole system is then critical (i.e., you can't stand to lose a single disk) until you rebuild the failed disk using the others. The rebuild process will potentially put more stress on the remaining drive(s) in a matter of hours than they would normally receive in a month, and may be accessing many sectors of the remaining disks that have not otherwise been accessed in a long time. If another disk is close to failure, then it is likely to fail during the critical rebuild process. I use RAID6 on two identical servers (no tapes, optical disks, etc.).
