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I have a dedicated machine (host) that will host two guests (Virtual Machines via KVM). What is better in regard to IO Performance:

Sorry, important update, by RAID I mean RAID-1 (and I will not have the possibility to change that...)

Should each VM have its own Partition (Raid1) where the "VM File Container" will be stored, or is it better to have ONE big Partition where both of these files will be stored? (I know that File Containers are not ideal in regard to performance but I will have to have File Containers...)

It would be kind if you can explain to me (or point me to some documents) what the relationship between partitions and performance are?

=>Does having several Partitions have an impact on the Disk and /or OS-Level for optimizing Read/Write Accesses for each Partition? Or is having several partitions maybe even slowing down everthing, as more diskseeks are required? How are Partitions organized? I assume this is one big continuous "block" of data.

So having a lot of smaller files using seperate partitions will most likely speed up the applications? As the files are placed after each and can be read in a single run. (But what is when both partitions with small files are accessed at the sime time, then also coslty diskseeks are required. Will these accesses be optimized to minimize diskseeks in different partitions?)

But when having only a few very large files (that are also precreated/preallocated) than several partitions do not have any positive effect, is this assumption correct?

Help and advice is very much appreciated, Thanks!! Jens

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1 Answer 1

up vote 1 down vote accepted

To my knowledge these 2 volumes would be near the same performance, the benefits come when using multiple disks to create the volume.

The optimal choice when working with on-board storage is raid 10 (4 disks), If only 2 disks were available for this project raid 0 (2 disks) a great performer but risky since no data redundancy.

Lastly another option is 2 separate disks as a dedicated volume for each vm.

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