On Mon, 26 Dec 2005, Tom Lane wrote:
...snip...
Thanks, it's a very good explanation!
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TIP 6: explain analyze is your friend
On Mon, Dec 26, 2005 at 12:32:19PM -0500, Alex Turner wrote:
It's irrelavent what controller, you still have to actualy write the
parity blocks, which slows down your write speed because you have to
write n+n/2 blocks. instead of just n blocks making the system write
50% more data.
RAID 5 must
Hello,
we have a PostgreSQL for datawarehousing. As we heard of so many
enhancements
for 8.0 and 8.1 versions we dicided to upgrade from 7.4 to 8.1. I must say
that the COPY FROM processes are much faster now from 27 to 17 minutes. Some
queries where slower, but the performance
At 08:35 AM 12/27/2005, Michael Stone wrote:
On Mon, Dec 26, 2005 at 10:11:00AM -0800, David Lang wrote:
what slows down raid 5 is that to modify a block you have to read
blocks from all your drives to re-calculate the parity. this
interleaving of reads and writes when all you are logicly
On Tue, Dec 27, 2005 at 05:09:28PM +0100, Albert Cervera Areny wrote:
However, now we have a query that is much slower with 8.1 compared to
7.4.
The query lasts 7minutes (all the times we try) with 8.1, keeping CPU usage
at 93~97% while it lasts 25 seconds in 7.4 the first time going
Historically, I have heard that RAID5 is only faster than RAID10 if
there are six or more drives.
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Ron wrote:
At 08:35 AM 12/27/2005, Michael Stone wrote:
On Mon, Dec 26, 2005 at 10:11:00AM -0800, David Lang wrote:
A Dimarts 27 Desembre 2005 18:13, Michael Fuhr va escriure:
On Tue, Dec 27, 2005 at 05:09:28PM +0100, Albert Cervera Areny wrote:
However, now we have a query that is much slower with 8.1 compared to
7.4. The query lasts 7minutes (all the times we try) with 8.1, keeping
CPU usage at
On Tue, 27 Dec 2005 19:02:17 +0100
Albert Cervera Areny [EMAIL PROTECTED] wrote:
Are there any rules of thumb to let a begginer give reasonable
values to these parameters? Not only work_mem, but also
random_page_cost, and so on. Are there any tests one can run to
determine good values?
On Tue, Dec 27, 2005 at 11:50:16AM -0500, Ron wrote:
Sorry. A decade+ RWE in production with RAID 5 using controllers as
bad as Adaptec and as good as Mylex, Chaparral, LSI Logic (including
their Engino stuff), and Xyratex under 5 different OS's (Sun, Linux,
M$, DEC, HP) on each of Oracle,
Bruce,
On 12/27/05 9:51 AM, Bruce Momjian pgman@candle.pha.pa.us wrote:
Historically, I have heard that RAID5 is only faster than RAID10 if
there are six or more drives.
I think the real question here is faster for what? Also, just like the
optimizer tunables for cpu/disk/memory speed
Bruce,
On 12/27/05 9:51 AM, Bruce Momjian pgman@candle.pha.pa.us wrote:
Historically, I have heard that RAID5 is only faster than RAID10 if
there are six or more drives.
Speaking of testing / proof, check this site out:
http://www.wlug.org.nz/HarddiskBenchmarks
I really like the idea -
At 02:05 PM 12/27/2005, Michael Stone wrote:
On Tue, Dec 27, 2005 at 11:50:16AM -0500, Ron wrote:
Sorry. A decade+ RWE in production with RAID 5 using controllers
as bad as Adaptec and as good as Mylex, Chaparral, LSI Logic
(including their Engino stuff), and Xyratex under 5 different OS's
On Tue, Dec 27, 2005 at 02:57:13PM -0500, Ron wrote:
Your quoted position is there isn't a 'RAID 5 penalty' assuming
you've got a reasonably fast controller and you're doing large
sequential writes (or have enough cache that random writes can be
batched as large sequential writes).
And you
At 04:15 PM 12/27/2005, Michael Stone wrote:
I don't understand why you keep using the pejorative term performance
hit. Try describing the performance characteristics instead.
pe·jor·a·tive( P ) Pronunciation Key (p-jôr-tv, -jr-, pj-rtv, pj-)
adj.
Tending to make or become worse.
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