VMAX striped meta-lun member limit

Question

I need to expand an 8-way metalun to a 12-way this weekend. Is this metalun config acceptable? is the member count to large? I tested the expansion and it worked ok, I'm just concerned about performance. Also, is there a tool to use to migrate this lun to a different size without needing a host reboot ? I have done a virtual lun migration on VMAX but that is to move a lun to a different thin pool. Cloning the lun is not an option right now since the host would need a reboot.

Thanks!

AranH1 · Accepted Answer

If you are using thin devices then it does not matter if the meta member count is not a power of two. The maximum members in a meta is 255 so you are still pretty far from that limit :-)

In thin provisioned environments we see performance benefits for some io type by increasing the meta member counts but the peformance benefits seem to taper off above 16 members so I usually don't build thin metas bigger than 16 members unless I need to do it for capacity reasons.

In thick provisioned environments using meta member counts in powers of 2 helped with the layout on the backend and had an impact on performance.

Zikas · Answer

Hi Daniel,

of course it is acceptable the 12-way-meta, but it is recommended to create metas in power of 2!!!

So i would suggest/recommend to do the 8-way-meta to 16-way-meta!!!!

i beilieve that other members of the ECN will agree with me..

Now regarding the VLUN migration, as you dais this mechanism is to move from a Thin Pool to another Thin Pool a tdev and not to migrate it to a new device.

Also in DMX the Optimizer do the same. Move a device from a Disk Group to another Disk Group.

Regarding migration try to use hosts tools migration such as in ESX use the Storage vMotion, in Unix try to us the Host Mirror copy, in Windows try to use PPME.

Quincy561 · Answer

Not too large.  I might think one above 64 members might be too many. Also powers of two was more important for thick volumes.  Not important for VP LUNs.

DanPJ · Answer

Sounds good, thanks!

VMAX

VMAX striped meta-lun member limit

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