Re: [Aoetools-discuss] AoE seems slow compared to iSCSI, what am I doing wrong ?

[Jesse B. <bec...@ma...>]

On Mon, May 09, 2011 at 01:33:39AM -0400, Tracy Reed wrote:
>On Sun, May 08, 2011 at 04:59:36PM +0200, Torbjørn Thorsen spake thusly:
>> I really want to stay away from the iSCSI setup,
>> but I'm at the end of my wits with regards to getting the required
>> performance from AoE.
>>
>> Any ideas as to what I'm doing wrong ?
>
>There are a few things you can do to help:
>
>1. Make sure you are using a good switch. Cisco, HP, I hear Juniper is good
>too. Anything else is likely to be crap. Netgear, Linksys, Dell are all right
>out.
>
>1. Make sure you use hardware flow control on the switch.

This is *really* important.  Check, and double-check again, that
flowcontrol is enabled.

>2. Double check that you really have mtu 9000 on both ends.
>
>3. I always run vblade with the -b 16384 option as without it performance was
>significantly less.
>
>4. Adding these to /etc/sysctl.conf helps a bit too:
>
># Optimizations to increase speed for AoE
>net.core.rmem_default = 278528
>net.core.rmem_max = 278528
>net.core.wmem_default = 278528
>net.core.wmem_max = 278528
>net.core.netdev_max_backlog=10000
>
># Don't let dirty write cache hang around so long, commit to disk sooner for
># safety. AoE targets can cache a lot of stuff.
>vm.dirty_ratio = 3
>vm.dirty_background_ratio = 3
>vm.min_free_kbytes = 65536
>
>The first stanza is for performance, the second for safety. Run /sbin/sysctl -p
>to make the system re-read sysctl.conf so the changes can take effect.
>
>And make sure you don't have any write alignment issues on the target disk. I
>used to try to partition my disk but that really complicates things
>alignment-wise so now I just initialize the raw disk (/dev/sdc for example) as
>an lvm physical volume and export an lvm from that.
>
>-- 
>Tracy Reed


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-- 
Jesse Becker
NHGRI Linux support (Digicon Contractor)