Re: hardare config question

We use the 3Ware BBUs and they¹re very nice, they self monitor and let you
know about their capacity if it¹s a problem.

- Luke

On 5/1/06 11:43 AM, "Erik Myllymaki" <erik(dot)myllymaki(at)aviawest(dot)com> wrote:

> good points, thanks.
>
> 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?
>>> >>
>>> >>
>>> >>
>>> >> Thanks.
>>> >>
>>> >> Mark Lewis wrote:
>>>> >>> It's also possible that the single SATA drive you were testing (or the
>>>> >>> controller it was attached to) is lying about fsync and performing >>>>
write
>>>> >>> caching behind your back, whereas your new controller and drives are
>>>> >>> not.
>>>> >>>
>>>> >>> You'll find a lot more info on the archives of this list about it, but
>>>> >>> basically if your application is committing a whole lot of small
>>>> >>> transactions, then it will run fast (but not safely) on a drive which
>>>> >>> lies about fsync, but slower on a better disk subsystem which doesn't
>>>> >>> lie about fsync.
>>>> >>>
>>>> >>> Try running a test with fsync=off with your new equipment and if it
>>>> >>> suddenly starts running faster, then you know that's the problem.
>>>> >>> You'll either have a choice of losing all of your data the next time
the
>>>> >>> system shuts down uncleanly but being fast, or of running slow, or of
>>>> >>> fixing the applications to use chunkier transactions.
>>>> >>>
>>>> >>> -- Mark
>>>> >>>
>>>> >>> On Fri, 2006-04-28 at 13:36 -0400, Vivek Khera wrote:
>>>>> >>>> On Apr 28, 2006, at 11:37 AM, Erik Myllymaki wrote:
>>>>> >>>>
>>>>>> >>>>> When I had this installed on a single SATA drive running from the
>>>>>> >>>>> PE1800's on-board SATA interface, this operation took anywhere
>>>>>> >>>>> from 65-80 seconds.
>>>>>> >>>>>
>>>>>> >>>>> With my new RAID card and drives, this operation took 272 seconds!?
>>>>> >>>> switch it to RAID10 and re-try your experiment. if that is fast,
>>>>> >>>> then you know your raid controller does bad RAID5.
>>>>> >>>>
>>>>> >>>> anyhow, I have in one server (our office mail server and part-time
>>>>> >>>> development testing box) an adaptec SATA RAID from dell. it is
>>>>> >>>> configured for RAID5 and does well for normal office stuff, but
>>>>> >>>> when we do postgres tests on it, it just is plain old awful.
>>>>> >>>>
>>>>> >>>> but I have some LSI based cards on which RAID5 is plenty fast and
>>>>> >>>> suitable for the DB, but those are SCSI.
>>>>> >>>>
>>>>> >>>> For what it is worth, the Dell PE1850 internal PERC4/Si card is
>>>>> >>>> wicked fast when hooked up with a pair of U320 SCSI drives.
>>>>> >>>>
>>>>> >>>>
>>>>> >>>>
>>>>> >>>> ---------------------------(end of
>>>>> >>>> broadcast)---------------------------
>>>>> >>>> TIP 3: Have you checked our extensive FAQ?
>>>>> >>>>
>>>>> >>>> http://www.postgresql.org/docs/faq
>>>> >>>
>>>> >>> ---------------------------(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
>>> >>
>>> >> ---------------------------(end of broadcast)---------------------------
>>> >> TIP 6: explain analyze is your friend
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>
>