I've noticed that the server is having intermittent severe lag today (occurs even when cloudflare is bypassed) when loading pages, thumbnails, and sample images. Original image downloads seem unaffected.

A few times today I've returned to the site only to find long multi-second delays loading the post page, and extremely sluggish sample image loading. Then around a minute later it goes back to being extremely fast with all pages and images loading near-instantly and stays that way for awhile.

Looking at your Munin graphs for ayase, it looks like there is something is causing Disk Utilization to get maxed out starting Monday when you reverted the site back to normal after April Fools. Hopefully this doesn't mean you've had another disk failure, and your RAID is degraded or rebuilding...