 | | | IBM RDAC (Multipath SAN failover) (Dag Wieers) | IBM RDAC (Multipath SAN failover) (Dag Wieers) 2004-12-07 - By Morten Sylvest Olsen
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On Mon, 6 Dec 2004, Morten Sylvest Olsen wrote:
>> I saw there was some discussion related to running the IBM RDAC
>>driver
>> on RHEL3. Anyone successfully running that configuration?
>>
>> I can very easily crash my box by running iozone on a md raid-1
>>drive
>> running on top of two drives visible through the RDAC driver.
>>
>> Configuration:
>>
>> IBM x345 2 x Xeon HT 2.5GB mem
>> IBM FastT 900 storage
>> 2 x QLogic Corp. QLA2312 HBA's
> What's important to know is what Qlogic driver you've been using.
>
> We've noticed a 30% decrease of performance when doing tests with the
> RDAC
> driver and since there's no real advantage of using the RDAC driver.
> We
> prefer the manual setup, it gives us control over how we're
> load-balancing
> and what systems are using which paths. (If you have 4 paths, you may
> want
> to balance your systems over 2 paths each).
Yeah, I saw performance improvement after removing the RDAC driver,
although it was hard to really test before because the machine chrashed
basically every time I was running iozone (or fsck! for that matter)
I'm using the v7.01.01 non-failover qlogic driver, which seems to work
well. I'm quite sure the error is with the RDAC driver. For example RAID
synchronization would stop midway because some of the io's seemed to be
stuck in the driver. Doing IO to the driver would kick it alive again.
During heavy I/O it would run out of memory and the machine would hang.
We have no choice but to go without RDAC, so I'll deffo look into your
configuration script.
- Morten
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