Hello,
Just a quick question
Usually from a PSERIES if you want to connect to IBM SAN Storage
you connect the IBM SAN Storage through a SAN Switch
something like this
---
however my question
Can you connect
from Pseries directly to San Storage without SAN Switch
what would be needed?
Thanks in advance.
it depends on FC HBA. afair newer FC HBAs doesn't support this option.
Even if it is possible it is perhaps not desirable anyway. Notice that the SAN switch is where you do the "zoning" - that is, in short: setting rules about which system gets to see which disks.
If you have exactly one SAN system and exactly one Managed System with one LPAR (where you wouldn't need zoning) the question arises why you would use a SAN instead of a simpler (and perhaps much cheaper) ordinary disk rack.
I hope this helps.
bakunin
bakunin,
I have in my testlab several old IBM SAN storages directly connected to several different LPARs, using my own ODM and drivers 
Hi,
Most HBA's will support the common standards that you would expect, IP over FC, Switched Fabric and Direct Connect. Where the issue tends to lie is the storage devices and the management tools, The IBM Shark or ESS products supported all the standards, the DS range does not support Direct Connect - but I think you may also have to implement a SVC with the DS range for IP over FC which is really a pretty dead standard now.
Regards
Gull04
Yes - but that is, as you say yourself, test equipment. My feeling is that filosophizer doesn't want to construct his own private playground. If he indeed does - you are right, why not?
bakunin
Thanks, the reason of not using ordinary disk rack, is the speed.
SAN Storage speed is much higher compared to ordinary disk speed
Example
making a tar backup on SAN Storage of 120GB takes 4 hours
making the same tar backup of regular disk take 16 hours
Then SAN Storage, has more data protection in case of power outage because of cache. So SAN Storage has more advantage.
So back to the question
Single Pseries with Two Fibre Card,
connect directly one HBA fibre card to Controller A
connect directly the other HBA fibre card to Controller B
I have not tried this yet, because I don't want Data correction, perhaps someone who has tried this can help me if it will work or not
Actually this is not really true. SAN may be faster than single disks, but you can create all sorts of striped disksets (RAIDs of various sorts), flash disks and caching controllers to achieve the same speed and throughput for a considerably lower price.
This is not to say that SAN is a bad idea in and of itself, but your setup seems to be intent not to use the advantages of a SAN anyway.
I hope this helps.
bakunin
I don't see why it would not work, however you are then limiting yourself for future growth. If you p-Series has two fibre cards and you have two free HBA on the SAN then you should just be able to cable them, but if you want to add another server, you have to make a choice:-
What is your likely future growth? If you are sure there is no growth then go ahead, but if you think you might replace your server at some point and might like to migrate the LUNs across, then you either have to have enough spare HBAs or invest in switches early is my recommendation.
Thinking about IO speed, it seems to be the write requests that work better. With local disk (not including hardware raid) the OS is directly responsible for ensuring that the write has been committed to the brown-spinning-stuff and must wait to get it done. With hardware RAID and SAN disk, you normally get a big chunk of cache. The OS writes to this cache and gets an acknowledgement that the write is complete. The server can then carry on and the disk array then completes the true write to the brown-spinning-stuff in it's own time to best economy based on physical head positions and rotation position of the disks.
I hope that this helps,
Robin
