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Re: [Xen-users] Image file or partitions over an iSCSI?

To: Ivan Porro <pivan@xxxxxxxxxxxxx>
Subject: Re: [Xen-users] Image file or partitions over an iSCSI?
From: Tomasz Chmielewski <mangoo@xxxxxxxx>
Date: Fri, 21 Sep 2007 15:18:19 +0200
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Ivan Porro schrieb:
Dear all,

I will setup soon an Infortrend iSCSI SAN device with a raid6 volume and a DELL PE1950 (8 VMs) with a Qlogic iSCSI HBA (server to be duplicated at later time for redundancy).

My priorities are:

1) VMs on the iSCSI SAN in order to boot them also by another server if the first one fails

2) performances

3) live migration is a non mandatory option (i.e. I can suffer to shutdown machines and restart them with minor service interruption, maybe with a heartbeat script)

My questions are:

The server(s) will have a raid 1 with two 74GB sas 15krpm drives.
Where do you would store your VMs?
You would use partitions (i.e. a LUN for each VM) or images?
Swap files could be on the local disks?

Surely partitions, or better yet, LVM volumes for flexibility.
Images won't allow you to do 1) (unless you set up and configure some fancy distributed fs). Also, file images are not very good from the performance side, but also, data integrity (you are more likely to suffer a filesystem corruption if that filesystem is kept in a file).

If you keep swap on a local disk, you won't be able to do a (live) migration. You can keep swap on a dedicated partition/LVM volume (available via iSCSI), or just use a swapfile, on the guest iSCSI partition (ext3 etc.).

Does a "local disk images and overnight mirror to the SAN" approach would be better in this case?

Sounds like "no", but I'm not sure what you really mean by the "overnight mirror to the SAN".

Religion question (optional...):

Waht would you prefere?

[ ] CentOS 5 with out of the box Xen
[ ] CentOS 5 with latest Xen
[ ] Debian 3.1 with latest Xen
[ ] Debian 4 with latest Xen

I'd use the latest Xen, with the latest OS version. Debian or CentOS, doesn't really matter I guess.

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