[ec2] Best practice for setting up MySQL on ubuntu?
admin at localeminder.com
Fri Sep 4 08:20:51 BST 2009
On Saturday 22 August 2009 14:51:09 you wrote:
> LocaleMinder.com wrote:
> > But our plan to prevent any downtime in the future is to bring LVM into the
> > mix. But our volume group will only ever contain the one EBS volume so we can
> > still use EBS snapshots. Basically we'll just use LVM to migrate from the
> > smaller volume to the larger volume.
> > David.
> Hi David,
> Before you guys commit to this method (assuming you have already
> tested it and found it will work for your needs), make sure you do run
> some tests. I used pvmove for the first time a month or two ago, and
> found it was very slow, all research pointed towards the simple and
> obvious fact that it must be an atomic operation, as it is actually
> "moving" the data if I recall correctly, not "copying" it leaving an
> "old copy" behind (for obvious reasons I'm guessing, but don't know why,
> meaning its not that obvious to me I guess), and it removes any kind of
> caching (that it is capable of removing) from the process.
> All of this was not on EC2, this was simply going from a 160GB Sata
> drive to a 500GB Sata drive, so I am not sure if EC2/EBS manages to
> speed up the process with caching that is hidden from LVM maybe. But
> testing the theory would be a good idea. And on the same token, if
> speed isn't an issue, then I guess its not a problem either. However, I
> don't like doing any kind of change to storage over long periods of time
> if I can avoid it, if you know what I mean. Obviously taking a backup
> before-hand would be the best bet as well (LVM is great for helping out
> with that! (shutdown MySQL, take LVM snapshot, restart MySQL, take
> backup of snapshot, voila)).
We haven't had time to test this yet and we haven't committed to it. I'm interested in your experience of pvmove though as I haven't used it on a live server yet. I don't think it's an issue that pvmove is slow as long as it doesn't prevent concurrent access to the disk by other processes and doesn't cause any corruption for said concurrency. I think I may ask the lvm mailing list before we pursue this too much further.
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