[Linux-cluster] Re: Storage Problems, need some advice

[Riaan van Niekerk]

> After doing much more research I came across the DS300 by IBM. It uses
> SCSI drives, is fully redundant, does iSCSI and doesn't cost an arm
> and a leg (just an arm). My question is, their site says linux
> clustering isn't supported, but does it have to be? Doesn't iSCSI let
> you do the same thing GNBD does?
> 

hi David

do you have a link to the page with that statement? "linux clustering" 
is somewhat of an ambiguous term. Within the context of Red Hat software 
(excluding Linux Virtual Server and high-performance computing 
clusters), it can mean either:

a) Cluster Suite (without GFS) - only one node in a cluster accesses the 
storage at a time. if you fail/switch over, one node unmounts an FS, 
another one mounts it.

b) GFS (which implies/includes Cluster Suite) - multiple nodes accessing 
   the same LUN with a (G)FS on top of it

I am not familiar with entry-level iSCSI initiators. I always thought 
iSCSI is logically like fibre, e.g. multiple hosts in the same raidgroup 
can concurrently access the same LUN/FS. Perhaps these entry-level iSCSI 
arrays are more like regular SCSI meaning that they do not support 
multiple initiators accessing the same LUN behind a target (storage 
processor).

I had a look at EMC cert matrix for the AX100/150 series arrays
http://www.emc.com/interoperability/matrices/AX_Series_SupportMatrix.pdf
thes entry-level EMC iSCSI arrays also only supports non-clustered Linux.

iSCSI will allow you to "do the same thing" as GNDB:
GNDB client and server are replaced iSCSI initiator (Linux host) and 
target (dedicated hardware, e.g. EMC array, or software target - not yet 
considered production-ready nor included with RHEL). However, if the 
hardware has an explicit exclusion of Linux clustering, you are stuck, 
not being able to have two nodes aaccess the storage at the same time..

HTH
Riaan

> Also, I talked to someone on their chat who said I could use any U320
> drive with it, basically I could reuse the drives I already have and
> just not use my old enclosure. Does that sound right? Any reason I
> couldn't do that other than loosing all my data?
> 
> Anyone using a DS300? Seems like with 15k drives it would be pretty darn 
> fast.
> 
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