LVM vs No-LVM?
Hi people.
I would setup soon a mysql server+php+apache, this server will run inside a vm with xen. Normally mysql run inside /var, this vm will have: 8GB RAM 64GB for this vm. The host will have Raid-10 with md. My question is, is better(disk speed) to setup this vm using the default layout lvm: Code:
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/ Hope u could understand my point, thanks!!! |
HI -
If you're running this thing in a VM, clearly a simple filesystem (eg. ext3 or ext4) should give you the better performance! IMHO .. PSM |
Thanks paulsm4 for your quick answer.
Last thing, went u say: Quote:
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I would use logical volumes, personally. I've never heard of LVMs causing a noticeable drop in performance.
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In the real world, with physical drives, sure.
In a VM, with an apparently I/O intensive application - no. I'd definitely recommend a simple filesystem. |
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So this really made me curious. I ran bonnie++ in two virtual machines, one used logical volumes and one just used a filesystem and regular partitioning. Here's the results.
Virtual Machine using LVM Code:
Version 1.03 ------Sequential Output------ --Sequential Input- --Random- Code:
Version 1.03 ------Sequential Output------ --Sequential Input- --Random- The first section (top portion of each test) is what we're interested in when talking about database performance, and the import part of that section is the block read/write section. The VM using logical volumes seemed to actually perform a little better, surprisingly. The VM using logical volumes had a block write speed of 43.9/MBs while the VM not using logical volumes had a block write speed of 40.4/MBs. With regards to block reads, the VM using logical volumes had a block read speed of 340/MBs while the VM not using logical volumes had a block read speed of 338/MBs. So it seems that the difference is negligible, but when you take into account the convenience of logical volumes I'd go that route. If anyone has any input and conflicting opinions or tests I'd love to see it. |
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Could the difference be explained by physical location on disk? Tracks located toward the outside of the platters would perform better than tracks nearer the centre. |
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