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тАО02-19-2009 10:44 PM
тАО02-19-2009 10:44 PM
I have MSA2000, only one controler(4.2 MSA2012FC) & one FC switch (SAN Switch 4/8). I have created 3 LUNs & they are maped to two hosts.
current case:
Host LUN FC Port 0 FC Port 1
HostA 0 Read-write Read-write
HostA 1 Read-write Read-write
HostA 2 Read-write Read-write
HostB 0 Read-write Read-write
HostB 1 Read-write Read-write
HostB 2 Read-write Read-write
Plan to do is
Host LUN FC Port 0 FC Port 1
Host A 0 Read-write no access
Host A 1 no access no access
Host A 2 Read-write no access
Host A 0 no access no access
Host A 1 no access Read-write
Host A 2 no access Read-only
Please reply is this possible? & how do I go abt it?
awaiting reply.
Solved! Go to Solution.
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тАО02-20-2009 12:10 AM
тАО02-20-2009 12:10 AM
SolutionYou don't write which operating system you use, but this almost never works:
- some file systems cannot be mounted read-only
- changes by Host A will not be seen by Host B 'immediately', because B assumes exclusive access to the volume, too. It does not expect that another server makes changes
Do NOT allow read-write access for both hosts unless you *know* you have a file system that really allows sharing of volumes. Please do *NOT* experiment! You DO risk losing data!
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тАО02-23-2009 01:57 AM
тАО02-23-2009 01:57 AM
Re: SAN switch host reassignment
Thanks for your valuable inputs.
I am detailing you with exact problem we are facing.
This is how our SAN was configured previously.
Host OS: WIN2K3 R2 Ent sp2
Host LUN FC Port 0 FC Port 1
Host A 0 Read-write Read-write
Host A 1 Read-write Read-write
Host A 2 Read-write Read-write
Host B 0 Read-write Read-write
Host B 1 Read-write Read-write
Host B 2 Read-write Read-write
Above configuration caused data corruptions on Lun├в ss as rightly said by you.
Current situation:- Host B access is dropped by disabling switch port & corresponding SAN port.
As a part of our change design which needs to be implemented, we have decided to reconfigure Host access as below.
Host LUN FC Port 0 FC Port 1
Host A 0 Read-write no access
Host A 1 no access no access
Host A 2 Read-write no access
Host B 0 no access no access
Host B 1 no access Read-write
Host B 2 no access Read-only
My worries are as below.
1) while doing this(reassignment) do I risk data loss? (Lun 1 which is currently used by host A will be used by host B after changes)
2) As LUN2 have read-write access for host A & read-only for Host B, will there be a time lag between data creation & data viewing especially from read only host.
3) Currently a switch FC port 5 is disabled for Host B, do I need to reactivate it before doing all these above changes?
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тАО02-23-2009 02:58 AM
тАО02-23-2009 02:58 AM
Re: SAN switch host reassignment
Like Uwe allready said.
sharing SAN-disks among servers that know nothing about eachother is a BAD idea.
This only works when some form of clustering software is used.
with windows-clustering, both hosts KNOW the disk is shared, so when one host is controlling the disk, the other keeps off!.
with an OS like tru64cluster there is a lock-manager, so the disk can really be shared among cluster-nodes.
depending on the windows-driver used and with two ports enabled you have either a failover-connection or a load-sharing connection
using only a single FC-port gives you no advantage.
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тАО02-23-2009 09:10 PM
тАО02-23-2009 09:10 PM
Re: SAN switch host reassignment
Thanks for your guidance.
I understand that you are talking about continuity point of view as one switch will not advantage & I will speak with seniors to go for another switch but we can't go hardware/software procurement in current scenario.
The current configuration is already messed-up & we have come out with the below solution with available hardware
Host LUN FC Port 0 FC Port 1
Host A 0 Read-write no access
Host A 1 no access no access
Host A 2 Read-write no access
Host B 0 no access no access
Host B 1 no access Read-write
Host B 2 no access Read-only
Please help me understand whether this solution will work or I am in a risk of loosing data.
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тАО02-24-2009 04:00 AM
тАО02-24-2009 04:00 AM
Re: SAN switch host reassignment
Please help me to resolve this isssue.
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тАО02-24-2009 04:17 AM
тАО02-24-2009 04:17 AM
Re: SAN switch host reassignment
2) There is no 'time lag'. Host B simply does not 'know' that the data can be updated by a different host so it will not attempt to refresh its file system view. It is even worse - due to unsynchronized access, host B could see inconsistencies which _can_ result in a crash of host B's operating system!
If you want host B to be able to access host A's data - use a simple file share.
3) No, volume presentation is completely independent from that.
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тАО02-26-2009 01:19 AM
тАО02-26-2009 01:19 AM
Re: SAN switch host reassignment
I have finally got the solution.
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тАО03-23-2009 01:06 AM
тАО03-23-2009 01:06 AM
Re: SAN switch host reassignment
Host LUN FC Port 0 FC Port 1
HostA 0 Read-write no access
HostA 1 no access no access
HostA 2 Read-write no access
HostA 0 no access no access
HostA 1 no access Read-write
HostA 2 no access Read-only
After performing above change I observed that LUN 2 has Read-write access from HostA but when I mapped same LUN to hostB as read-only as mentioned in above chart 3rd & 6th line, it' not accessible from hostB.
It shows as drive in my computerbut do not display properties & while trying to access gives error as"No media is write protected"
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тАО03-23-2009 01:21 AM
тАО03-23-2009 01:21 AM