2.6.20: stripe_cache_size goes boom with 32mb

From: Justin Piszcz
Date: Fri Feb 23 2007 - 06:42:30 EST

Each of these are averaged over three runs with 6 SATA disks in a SW RAID 5 configuration:

(dd if=/dev/zero of=file_1 bs=1M count=2000)

128k_stripe: 69.2MB/s
256k_stripe: 105.3MB/s
512k_stripe: 142.0MB/s
1024k_stripe: 144.6MB/s
2048k_stripe: 208.3MB/s
4096k_stripe: 223.6MB/s
8192k_stripe: 226.0MB/s
16384k_stripe: 215.0MB/s

When I tried a 32768k stripe, this happened:
p34:~# echo 32768 > /sys/block/md4/md/stripe_cache_size
Connection to p34 closed

I was able to Alt-SysRQ+b but I could not access the console/X/etc, it appeared to be frozen.



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