On Mon, 2006-05-01 at 13:22, Tom Arthurs wrote:
> UPS does not protect against the tech behind the rack unplugging the
> power cable, or an accidental power cycle from exercising the wrong
> switch. Both are probably more common causes of failure than a total
> power outage.
>
> Erik Myllymaki wrote:
> > I have been in discussion with 3ware support and after adjusting some
> > settings, the 3ware card in RAID 1 gets better performance than the
> > single drive. I guess this had everything to do with the write (and
> > maybe read?) cache.
> >
> > Of course now i am in a dangerous situation - using volatile write
> > cache without a BBU.
> >
> > If I were to use a UPS to ensure a soft shutdown in the event of power
> > loss, am I somewhat as safe as if I were to purchase a BBU for this
> > RAID card?

Nor does it prevent an electrician from dropping a tiny piece of wire
into a power conditioner, causing a feedback that blows the other two
power conditioners, all three industrial UPSes, and the switch that
allows the Diesal generator to take over.

When that happened to me, I had the only database server in the company
to come back up 100% in tact. You can guess by now I also had the only
database server with battery backed cache...

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guess who just bought a 3ware BBU on ebay...

Thanks for all the posts, consider me educated!

(on the importance of BBU on RAID controllers, anyway)




Scott Marlowe wrote:
> On Mon, 2006-05-01 at 13:22, Tom Arthurs wrote:
>> UPS does not protect against the tech behind the rack unplugging the
>> power cable, or an accidental power cycle from exercising the wrong
>> switch. Both are probably more common causes of failure than a total
>> power outage.
>>
>> Erik Myllymaki wrote:
>>> I have been in discussion with 3ware support and after adjusting some
>>> settings, the 3ware card in RAID 1 gets better performance than the
>>> single drive. I guess this had everything to do with the write (and
>>> maybe read?) cache.
>>>
>>> Of course now i am in a dangerous situation - using volatile write
>>> cache without a BBU.
>>>
>>> If I were to use a UPS to ensure a soft shutdown in the event of power
>>> loss, am I somewhat as safe as if I were to purchase a BBU for this
>>> RAID card?
>
> Nor does it prevent an electrician from dropping a tiny piece of wire
> into a power conditioner, causing a feedback that blows the other two
> power conditioners, all three industrial UPSes, and the switch that
> allows the Diesal generator to take over.
>
> When that happened to me, I had the only database server in the company
> to come back up 100% in tact. You can guess by now I also had the only
> database server with battery backed cache...
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match

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TIP 6: explain analyze is your friend