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Re: ext3 on RAID1 gains very little?



On Thu, 23 Oct 2003, Vijayan Prabhakaran wrote:
> under what journaling mode you're running ext3 - data=journal or
> data=ordered ?

'data=ordered', unless someone changed the default on me recently. I
also have 'noatime' and the largest possible journal, so it /shouldn't/
be contention on that.

> note that if you have mirroring under full journaling, every write is
> going to take 4 write i/os - 2 mirrored writes for the journal and 2
> mirrored writes for the actual data.

*nod*  Very little write load occurs during this period, less than 1 meg
total. Fully journaled data is too heavy for a software RAID1, I think,
at least when you have an hour of built-in UPS. :)

> but you seem to have this high load when starting a session and may be
> the reads are not giving the full bandwidth. in raid-1, if the reads
> are sequential they are directed to only one mirror. that may be the
> reason why the second drive is almost idle.

For starting a single task, I see this. Starting a static opera, XEmacs
and Lotus Notes under Wine, though, involves data that is ... widely
scattered across my disks. :)

          Daniel

-- 
Time spent in the advertising business seems to create a
permanent deformity like the Chinese habit of foot-bonding.
        -- Dean Acheson




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