[lug] Software RAID5 performance

Sean Reifschneider jafo at tummy.com
Sun Nov 14 18:14:29 MST 2004


On Sat, Nov 06, 2004 at 07:04:52PM -0700, David Anselmi wrote:
>cache.  So when you copy them all the kernel does is adjust it's 
>accounting to map the original blocks to new (additional) inodes.  You'd 

Doubtful, since it sounded like the copy was being done across filesystems
(copying from the tmpfs to the disc), and inodes don't cross filesystem
boundaries.  That's why you can't "ln" across mountpoints.

The real problem is the data-set size.  The rule of thumb is to always use
a data-set which is at least twice the size of the physical RAM on the
system for doing disc performance testing.  That way you're sure that your
blocks probably aren't getting cached.

Sean
-- 
 Some girl with psychic power, She said "T-bone, what's your sign?"
 I blinked and answered "Neon", I thought I'd blow her mind.
Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995.  Qmail, Python, SysAdmin



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