RAID 1. 0 or RAID 5 for multiple VMs - what is the best choice? If this is a mission critical system, then you need to make sure that you've got some spare drives locally should one fail (unless you have some support contract on the hardware that says you can get replacements same- day, but even then a local spare is worth having). Ignoring that (or assuming the six drives doesn't count spares you might have easy access to) I would suggest RAID1. RAID1s nested in a RAID0) over RAID5 for the performance reasons you mention. Or if space is not at all an issue and redundancy and rebuild- on- drive- failure time is a big concern, then you might even consider two three- drive RAID1s nested in RAID0 (but that is overkill for most purposes, though it would allow two drives on each R1 leg to fail at the same time while keeping the array alive). There is another option though: three separate RAID1 arrays (or possibly two RAID1. RAID1. 0 (RAID1. E as some controllers call it)). This way you can spread the VMs over different spindles so they will compete with each other far less for IO bandwidth. Two VMs on different RAID1 arrays can be merrily thrashing their virtual disks without much affecting the responsiveness of each other or a VM on the third array. Of course this can end up being wasteful space- wise: you may end up with a lot of free space on one array but don't want to use it as there are already I/O intensive VMs in constant use on that array for instance (though in this case if you had a single array the VM you would put in that space would be competing for IO access like that anyway), or you may end up with 2. Gb free on each array but need 5. Gb for a new VM. This technique can make a lot of difference with spinning- disk- and- arm based drives if you balance your VMs between the drives right. ![]() It's pretty straight forward installing Ubuntu Server 16.04 on hardware RAID, but what if you want to use software RAID instead? It still makes a difference on SSDs too, but less so as you do not have the head movement and waiting- for- the- right- sector- to- pass- by issues causing extra performance killing latency. Though as I said above, it can be more work to manage. In the use case you describe, you might put that lightly loaded sharepoint server and the build- master on one array and the development VMs on another (possible one array each, if you have three arrays and no other active VMs). As needs change you can always move the VMs around the arrays to rebalance the load with little down- time (no down- time at all if your chosen virtualisation solution supports live migrations between local data stores). In this article we will explain how to install, maintain and use MS SQL Server on RHEL / CentOS and Ubuntu Server.
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November 2017
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