Re: SAN performance

I'm about to do a whole bunch of testing here on various DA element
sizes, and datablock sizes and how the affect pg performance. It doesn't
appear possible to get > 4kb filesystem blocks under linux due to the
limitation of the pagesize. We're running AMD64 for these tests, but the
DA configuration should be pretty much identical for IA32.

My best guess right now is that recompiling pg with a 4kb datablock
size, and using 4kb filesystem blocks with an 8 sector (4kb) element
size is probably the way to go for an active database.

Contact me off-list if you want a copy of the EMC CLARiiON "Best
Practices for Fiber Channel Storage" white paper. Haven't read it since
I only got my copy this morning, but... looks promising.

Drew

Anjan Dave wrote:

> I believe 1/0 or 1+0 is aka RAID-10. CX300 doesn't support 0+1.
>
> So far i am aware of two things, the cache page size is 8KB (can be increased or decreased), and the stripe element size of 128 sectors default.
>
> Thanks,
> Anjan
>
> -----Original Message-----
> From: Mr Pink [mailto:mr_pink_is_the_only_pro(at)yahoo(dot)com]
> Sent: Thu 9/23/2004 11:39 AM
> To: Anjan Dave; pgsql-performance(at)postgresql(dot)org
> Cc:
> Subject: Re: [PERFORM] SAN performance
>
>
>
> Hi,
>
> I expect you mean RAID 1/0 or 1+0 since the CX300 didn't support RAID 10 last time I looked.
>
> Whether you are using a SAN or not, you should consider putting the WAL files (pg_xlog folder) on
> seperate diskes from the DB. Since the log files are mostly written to, not read from you could
> just use RAID 1.
>
> It's a pity pg doesn't have a way to use a cluster of servers to get the most out of your
> expensive SAN.
>
> I read a comment earlier about setting block sizes to 8k to math pg's block size. Seems to make
> sense, you should check it out.
>
> Have fun,
> Mr Pink
>
> --- Anjan Dave <adave(at)vantage(dot)com> wrote:
>
> > Hello,
> >
> >
> >
> > I'll be moving a DB from internal RAID-10 SCSI storage to an EMC CX300
> > FC RAID-10 LUN, bound to the host. I've setup a test host machine and a
> > test LUN. The /var/lib/pgsql/data folder is sym-linked to a partition on
> > the LUN.
> >
> >
> >
> > Other than the shared_buffers, effective cache size, and sort memory, I
> > am not sure if I need to change any other parameters in the
> > postgresql.conf file for getting maximum performance from the EMC box.
> >
> >
> >
> > Is there a general guideline for setting up postgres database and the
> > tunable parameters on a SAN, especially for EMC?
> >
> >
> >
> > Appreciate any help,
> >
> >
> >
> > Thanks,
> > Anjan
> >
> >
>
>
>
>
>
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