Kinkie wrote:
On Wed, Mar 26, 2008 at 3:30 PM, Marcus Kool
<marcus.kool@xxxxxxxxxxxxxxx> wrote:
The point of why I started the discussion is that the statement in the wiki
"Do not use RAID under any circumstances" is at least outdated.
Well, it says: "Don't". Agreed, it's a bit radical. You're welcome to
edit the wiki if you wish, just let me know your wiki username so that
I may give you write access.
OK, I am willing to to the edit and also include the VRRP/JBOC as an alternative.
My Wiki name is "Marcus Kool".
Most companies will trade in performance for reliability because they depend
on internet access for their business and cannot afford to have 2-48 hours
of unavailability.
I'm not going to argue with that. The point is that usually there are
more cost-effective ways to get the same level of reliability if not
more.
For instance, going JBOC (Just a Bunch Of Caches) with
load-balancing/high-availability mechanisms (Proxy PAC/WPAD or Linux
Virtual Server with or without VRRP or any other Layer 2-4 load
balancing solution) is a very effective system to get very high
reliability.
Everybody knows that EMC and HP systems are much more expensive than
a JBOD but this is not a valid reason to say "Never use RAID".
"Never use RAID" implies that RAID is *BAD* which is simply not true.
From my point of view, the wiki should say something like:
If you want cheapest, modest performance, with no availability guarantees use JBOD.
If you want cheap, modest performance and availability use RAID1/RIAD5 without
a sophisticated disk array (preferably with a RAID card that has
128+ MB battery-backed write cache).
If you want cheapest availability use RAID5 without a sophisticated disk array
If you want expensive extreme performance and availability use a sophisticated disk array.
Agreed, it can be improved. The point that should be driven across is
that rather than spending 1kEur for a HW RAID SCSI Controller + 5KEur
for the disks to go with it, it's much more cost-effective to spend
2KEur for a second server and use VRRP.
