So recently I deployed 3 XenServer 6 hosts with local storage only. Our need was to virtualize approx 6 very old Centos QA servers running on ancient hardware. Since I did not have any dedicated network/san storage at my disposal I stuck 6, 146 SAS drives in each server and carved them up into a 410GB raid 10 array. However the XenServer install did not detect this secondary logical disk, so I had to figure out how to manualy create a storage repository using this new drive.
lun
Add a New Disk/Lun to RHEL5/CentOS5 without Rebooting
Anyway the command below causes a rescan of the scsi bus which is what you need to do for your server to detect a newly added disk. I find myself doing this on virtual machines all the time. Oh and for the love of all that is holy, please create your new disk a logical volume, and dont be lazy and just format the disk and stick a filesystem on it.
Resolving SCSI Reservation Conflicts/Locks in Vsphere 4.0
A few days ago we got hit with a ton of alerts which indicated that a handful of VMs were down, then up, and down again. This cycle continued several times. At first, after a bit of digging through logs, we thought that the issue was related to scsi reservation errors, but we were already … Continue reading Resolving SCSI Reservation Conflicts/Locks in Vsphere 4.0
Raid Levels Explained and Simplified
First off its important to know that RAID stands for either "Redundant Array of Independent Disks", or more commonly "Redundant Array of Inexpensive Disks". Either way you slice it (pun intended) the basic idea of RAID is to combine multiple hard disks to either increase performance or increase redundancy. Before I get started its important to introduce the term LUN. A LUN is a logical disk that consists of raw physical disk space. LUNs are created as a basic part of the storage provisioning process. They are presented across a SAN to a server as a single physical disk. Note that the title of this article is "Raid Levels Explained and Simplified", and when I say Simplified I mean it. I am going to give a brief overview of most of the common RAID levels and then present a weakness and strength.