Re: Bad iostat numbers

The RAID 10 was in there merely for filling in, not really as a compare,
indeed it would be ludicrous to compare a RAID 1 to a 6 drive RAID 10!!

How do I find out if it has version 2 of the driver?

This discussion I think is important, as I think it would be useful for this
list to have a list of RAID cards that _do_ work well under Linux/BSD for
people as recommended hardware for Postgresql. So far, all I can recommend
is what I've found to be good, which is 3ware 9500 series cards with 10k
SATA drives. Throughput was great until you reached higher levels of RAID
10 (the bonnie++ mark I posted showed write speed is a bit slow). But that
doesn't solve the problem for SCSI. What cards in the SCSI arena solve the
problem optimally? Why should we settle for sub-optimal performance in SCSI
when there are a number of almost optimally performing cards in the SATA
world (Areca, 3Ware/AMCC, LSI).

Thanks,

Alex

On 12/4/06, Scott Marlowe <smarlowe(at)g2switchworks(dot)com> wrote:
>
> On Mon, 2006-12-04 at 01:17, Alex Turner wrote:
> > People recommend LSI MegaRAID controllers on here regularly, but I
> > have found that they do not work that well. I have bonnie++ numbers
> > that show the controller is not performing anywhere near the disk's
> > saturation level in a simple RAID 1 on RedHat Linux EL4 on two
> > seperate machines provided by two different hosting companies. In one
> > case I asked them to replace the card, and the numbers got a bit
> > better, but still not optimal.
> >
> > LSI MegaRAID has proved to be a bit of a disapointment. I have seen
> > better numbers from the HP SmartArray 6i, and from 3ware cards with
> > 7200RPM SATA drives.
> >
> > for the output: http://www.infoconinc.com/test/bonnie++.html (the
> > first line is a six drive RAID 10 on a 3ware 9500S, the next three are
> > all RAID 1s on LSI MegaRAID controllers, verified by lspci).
>
> Wait, you're comparing a MegaRAID running a RAID 1 against another
> controller running a 6 disk RAID10? That's hardly fair.
>
> My experience with the LSI was that with the 1.18 series drivers, they
> were slow but stable.
>
> With the version 2.x drivers, I found that the performance was very good
> with RAID-5 and fair with RAID-1 and that layered RAID was not any
> better than unlayered (i.e. layering RAID0 over RAID1 resulted in basic
> RAID-1 performance).
>
> OTOH, with the choice at my last place of employment being LSI or
> Adaptec, LSI was a much better choice. :)
>
> I'd ask which LSI megaraid you've tested, and what driver was used.
> Does RHEL4 have the megaraid 2 driver?
>