On Tue, Jun 17, 2008 at 05:10:10AM -0700, HIMANSHU wrote:
> 1.
> You say that performance figures are this..
> single iSCSI session:
>     * 450MB/s Read and 450 MB/s Write for 64KB block
>     * 510 MB/s Read and 550 MB/s Write for 256KB block
>     * 65,000 IOPS - 1K, 58,000 IOPS - 2K, 50,000 IOPS with 4KB Read
> two iSCSI sessions:
>     * 550 MB/s Read and 810 MB/s Write for 256KB block
>     * 75,000 IOPS for 1K block
> How can we measure figures on our machine?
> "Iometer" , "disktest" are few tools available for that.
> Can u suggest any good one?

I've used 'iozone' but you can also just do variations of 'dd' with different
block sizes. And play around with changing the MTU.

> -------------------------------------------------------------------------------------------------------------------------------
> 2.
> When Initiator can get access to disk from target,What all
> applications user can have?Means besides Storage,what is the use of
> this Disk?

None. It is just as a normal disk.

> --------------------------------------------------------------------------------------------------------------------------------
> 3.
> If one initiator is logged in to target "iqn.
> 2008-06.com.companyname:BLOCKIO_TARGET" which is 1 GB.
> It thus have access to it,it partitions it using "fdisk".Creates file
> system using "mkfs".mounts it and writes 300 MB data on it.
> If second initiator machine logs in to the same target,it can view all
> the 300 MB data written by 1st initiator if 2nd initiator doesn't
> format that disk after login. 2nd initiator only mounts the logged in
> disk and thus had access to all the 300 MB data. Is it ethical?

You can do it but without using a proper filesystem that can deal with
multiple writers/readers it will be hosed. Look in using 'gfs2' filesystem
(or GFS from Red Hat, or GPFS from IBM) along with the cluster componenents
to synchronize the disk usage.

You might be tempted in thinking that you can mount from one initiator
the disk as read-only with 'ext3' or 'ext3' - but from what I've heard
that still leads to errors.

> Should we allow same target to be shared by multiple initiators at the
> same time?

If you want to use Xen and transition between nodes then yes you want
to use it.

Also for clustering software this can be used - where there is a shared

> What will be the pros and cons?

Look up on Google 'cluster software pros' to find that out.

> I think,we need to handle synchronization issues there.Data written by
> 1st initiator shouldn't be deleted by others and all......
> Or Data from 1st initiator should not be visible/accessible to others.
> What approach looks more ethical and practical?

Use cluster software. 

> -------------------------------------------------------------------------------------------------------------------------------

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