• I'm installing OES 2 SP3 in a DomU to support 10 users.
  • I want to use NSS.
  • The Hardware is a dual Xeon system with Seagate Enterprise SATA drives - on a UPS.
  • In Dom0, sda & sdb are software RAID1. (Dom0 & DomU OS)
  • In Dom0, sdb & sdc are software RAID1. (for NSS in a DomU)
  • In Dom0, I have created Logical Volumes on the RAID devices and present them to the DomU as Block Devices.

I have used this configuration for small systems before without any issues. I understand there are performance limitations when using SATA drives but I'm a bit puzzled by these statements in the OES 2 Planning and Implementation Guide for OES 2 SP3:

6.18 Virtualization Issues

The following are caveats for setting up OES 2 server in Xen VMs:

6.18.5 NSS Considerations

Make sure you follow these guidelines for using NSS volumes in connection with OES 2 servers running in Xen VMs:
  • Both Linux and NetWare Platforms: NSS pools and volumes must be created on only SCSI or Fibre Channel devices. You cannot use a file-based disk image, LVM-based disk image, or an SATA/IDE disk for the virtual machine.
The OES 2 SP3: NSS File System Administration Guide for Linux has a slightly different explanation:

6.1.2 Virtual Machine Issues

Assigning Physical Disks or Disk Partitions to the Virtual Machine

For the best performance on a Xen guest server, NSS pools and volumes should be created on block storage devices that are local SCSI devices, Fibre Channel devices, iSCSI devices, or partitions on those types of devices.

SATA or IDE disks have slower performance because special handling is required when working through the Xen driver to ensure that data writes are committed to the disk in the order intended before it reports back.

Assigning File-Backed Disk Images for Virtual Devices

Novell supports file-backed disk images on virtual machines, but does not recommend using them for important data because the volume can become corrupt after a power failure or other catastrophic failure. For example, file-backed volumes might be useful for training and sales demonstrations.

Every OES document that discusses an NSS implementation in a DomU has a slightly different explanation. The inconsistancies in the explanations raise the following questions:
  • Is there some new evidence that shows SATA drives to be unreliable or is it simply a question of performance?
  • Is the comment about file-backed-storage valid? Does it only apply to NSS?