[linux-lvm] pvmove speed

Roy Sigurd Karlsbakk roy at karlsbakk.net
Sat Feb 18 08:12:01 UTC 2017

>    200-500... impressive for a SAN... but considering the bandwidth
> you have to the box (4x1+10), I'd hope for at least 200 (what I get
> w/just a 10)... so must be some parallel TCP channels there... he..
> What showed those speeds?  I'm _guessing_, but its likely that pvmove
> is single threaded.  So could be related to the I/O transfer size as
> @pattonme was touching on, since multi-threaded I/O can slow things
> down for local I/O when local I/O is in the .5-1GBps and higher range.

Well, it’s a Compellent thing with net storage of around 350TiB, of which around 20 is on SSDs, so really, it should be good. Tiering is turned off during migration of this data, though (that is, we’re migrating the data directly to a low tier, since it’s 40TiB worth of archives).

>    Curious -- do you know your network's cards' MTU size?
> I know that even w/1Gb cards I got 2-4X speed improvement over
> standard 1500 packets (run 9000/9014 byte MTU's over local net).

Everything’s using jumboframes (9000) on the SAN (storage network), and it’s a dedicated network with its own switches and copper/fiber. The rest of the system works well (at least the Compellent things, EqualLogic has a bad nervous breakdown on its way to the cemetery, but that’s another story. The Exchange servers running off it, gave us around 400MB/s (that is, wirespeed) last backup. That wasn’t raw i/o from vmware, this is, but then again, I should at least be able to sustain a gigabit link (the EQL storage is hardly in use anymore, perhaps that’s why it’s depressed), and as shown, I’m limited to around half of that.

Vennlig hilsen / Best regards

Roy Sigurd Karlsbakk
(+47) 98013356
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Da mihi sis bubulae frustrum assae, solana tuberosa in modo Gallico fricta, ac quassum lactatum coagulatum crassum. Quod me nutrit me destruit.

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