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Am Donnerstag 12 Juli 2007 16:14 schrieb M. Edward (Ed) Borasky: |
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> Florian Philipp wrote: |
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> > Hi! |
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> > |
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> > I've got two questions concerning LVM2. |
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> > |
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> > Number one: What stripesize parameter would you use? The manual of my |
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> > mainboard advises to use 64k for a RAID-0. Would that be useful for my |
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> > portage tree or a more conventional partition like /usr and /var? |
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> > |
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> > Number two is not really a performance issue but it's LVM2-related: |
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> > LVM2-mirrors need an extra log device but the man pages don't tell |
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> > anything about how large it has to be or if it can be a partition or loop |
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> > device on the same hdd as one of the mirrors. |
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> > |
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> > Thanks in advance! |
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> > |
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> > Florian Philipp |
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> |
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> Sizing I/O subsystems is highly workload and filesystem dependent, and |
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> there's really no such thing as a one-size-fits-all quick answer. There |
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> are models and there are some really good I/O subsystem benchmarks you |
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> can use once you know what your workload characteristics are. |
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> |
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> I highly recommend the book "Storage Network Performance Analysis" |
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> http://www.amazon.com/Storage-Network-Performance-Analysis-Huseyin/dp/07645 |
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>1685X/ for the tools to do this. But one thing you can do first is to run |
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> your workload on a system and capture data with "iostat". If you don't have |
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> "iostat", you'll need to emerge "sysstat". The "iozone" benchmark is in |
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> Portage, as is bonnie++. The I/O benchmark I like most is IOMeter, but that |
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> requires a Windows system to run the control console and |
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> downloading a Linux agent from their web site. |
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Thanks for the tips! |
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Just for the record: |
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I've solved problem number two: The log is not bigger than a few MB for 20GB |
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of storage space. To create it you have to use two commands: |
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|
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At first, you create the mirror without log device: |
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lvcreate -n $Name -L $Size -m $Number_of_mirrors --corelog $Volume_group |
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Then you use lvconvert to attach a log and to create it anywhere: |
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lvconvert $Volume_group/$Logical_volume -m $Number_of_mirrors --alloc anywhere |
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Using "--alloc anywhere" with lvcreate is not wise because lvcreate tries to |
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create all volumes on one device, then. |
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Regards, |
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|
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Florian Philipp |