Re: Advantages and disadvantages of more than one dbserver

On Fri, 4 Jul 2003, Daniel Seichter wrote:

> Hello Sam and Scott
> > We'll be looking at more performance boosts once the system is mature.
> > We already have the DB on a dedicated drive, on a dedicated controller.
> > Moving to a RAID 1 config with another 120GB drive would be good. The DB
> > on disk currently takes up about 35GB with only 1 quarters data, but
> > growth with longer timespans should be minimal as the DB is very well
> > normalised. RAID 5 not an option in the current box, as there are not
> > enough bays in the (crappy RM desktop) case, and we'd have to use
> > software RAID or buy a more epensive controller, and probably move to
> > SCSI, which would be expensive enough to justify buying a small
> > dedicated box instead, which would be better in many ways. When ones
> > workstation is also supposed to be a high-availability server, certain
> > things become difficult.
> Is there any knowned rate in percent, how much faster a database will be if
> I would put 1GB instead of 512MB into my server?
> What RAID do you prefer? A 'simple' RAID1 should be enough or do you prefer
> RAID5 or what else?

Well, it really depends on the size of your data set.  If you've got a 100
Meg database, then going from 512Meg to 1Gig is likely a waste.  As long
as your dataset is larger than how much your kernel can cache given the
current memory size, then you can see a performance gain from more memory.

RAID-1 versus RAID-5

Generally RAID-1 is faster, especially for a smaller number of concurrent
users.  As your number of concurrent processes rise, you can look at using
something like RAID 1+0 / 0+1 to increase the number of platters, or
RAID5.  While 1+0 / 0+1 will usually be faster, they will provide less
storage per disk used, whereas RAID5 will provide better economy (n-1
storage) but slightly lower write performance than many RAID1 or 1+0
setups.

RAID5 will, however, provide very good read performance under parallel
load, so for data warehouses or mostly read sites, RAID5 is a good choice.
For heavy transactional load look at RAID1 or 1+0.