Re: [Xen-users] Planning - question about storage

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

2009/6/11 Werner Flamme <werner.flamme@xxxxxx>:
> Hi everyone,
>
> I am very new to Xen but will migrate 3 SAP ERP servers plus 1 SolMan
> into a Xen environment next year, probably running Novell's SLES (as we
> use SLES right now).
>

Wow, you're the first person I know that will be running SAP on top of
Xen. Let us know how it goes.

AFAIK since SAP license cost is much more expensive compared to
hardware cost, hardware savings (thru virtualization, for example)
will be insignificant compared to license cost, so we focus saving
efforts on license.

> The machines will be app servers only, no DB - the DB is "outsourced" to
> a common Oracle RAC this year (maintained by a colleague).
>
> So I will get 2 boxes and now fiddle around with possible configuration
> of storage. Due to SAP notes the SAP binaries must be stored on the RAC
> and made accessible from there, for example via NFS or SAN. In our
> company, we are used to SANing ;-), so my boxes will have some FC boards
> to connect to the RAC's 2 FC switches. Am I right that I can access the
> block device from SAN (will be one big thing with OCFS2) inside dom0 and
> pass them via phy: to the domUs?

And use OCFS2 on domU? should be possible. Although it'd be simpler if
you import it via nfs on domU.

>
> Next: the OS of the domU. I plan to have some local disk space (about
> 300 GB per box). I think on something like a drbd drive (RAID-1) that is
> separated into chunks for each domU. The dom0 forwards the respective
> part to the domU. The domUs use this disk space for their operating
> system. Somewhere (like in /bigthing/) the big shared storage is mounted
> and the necessary symlinks for SAP are set.
>

I still have doubts against drbd, but other user has reported it gives
acceptable performance, so you may want to search the list archive for
his particular setup.

If it were me I'd simply put domU's storage on SAN if I need migration
(you already have SAN anyway, right?) or on mirrored local disk (for
maximum I/O throughput)

-- 
Fajar

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