A meta device is a Symmetrix mechanism for creating a device larger than the current maximum hyper volume size (262668 cylinders or 240GB on EMC Symmetrix VMAX). There are two types of meta devices – concatenated or striped.
For virtual provisioned environment, concatenated meta volumes are recommended by EMC, striped meta is not recommended.
Given below are the steps to create a concatenated meta device and expand the meta device on an EMC symmetrix VMAX system using symcli
In this example, we are using hypers 0010, 0011 and 0012 for creating the meta and 0013 to expand the already available meta.
To form the meta for the first time, the meta head (in this case 0010) should not be mapped to any front end ports. If it is mapped, unmap the hyper before proceeding. Also, the meta tails (0011 and 0012) should not be attached to any FAs (unmapped) and the data will be lost.
symconfigure –cmd “form meta from device 0010, config=concatenated; add dev 0011:0012 to meta 0010;” prep
Once the above command completes successfully, commit the changes
symconfigure –cmd “form meta from device 0010, config=concatenated; add dev 0011:0012 to meta 0010;” comm
To add hyper 0013 to already formed meta device 0010 (meta head), execute the following command
symconfigure –cmd “ add dev 0013 to meta 0010;” prep
Once the above command completes successfully, commit the changes
symconfigure –cmd “ add dev 0013 to meta 0010;” comm
Expanding striped meta device is bit more complicated, click here for procedure
Can you provide me the reference where emc says that stripped meta is not recommended for vp?
ReplyDeleteHi Terry
DeleteI have seen this recommendation in one of the EMC training slides. There may be other documentation out there which explains it as well. Given below is the extarct from the training slide.
"© 2009 EMC Corporation. All rights reserved. Device Creation and Mapping - 10
Striped vs. Concatenated Meta
Usually, striped meta volumes will perform better than concatenated
ones
– Because they reside on more spindles.
– If there are not enough drives for all the meta members to be on separate
drives consider concatenated.
– If host striping is planned, concatenated meta volumes may be better
Concatenated Meta Volumes can be placed on the same RAID
group
– Can create a reasonable emulation of a native large volume on Symmetrix
DMX systems or Symmetrix V-Max systems
Don’t place striped meta volumes on the same RAID group
(wrapped)
For Virtual Provisioning environments, concatenated meta volumes
work better
– (Thin Meta Volumes)
Striped meta volumes perform better than concatenated meta volumes when there are enough spindles
to support them. However, if the striping leads to the same physical spindle hosting two or more
members of the meta volume, striping loses its effectiveness. In such a case, using concatenated meta
volumes is better.
It is not a good idea to stripe on top of a stripe. Thus, if host striping is planned and meta volumes are
being used, concatenated meta volumes are better.
In Virtual Provisioning environments it is advisable to use concatenated metavolumes© 2009 EMC Corporation. All rights reserved. Device Creation and Mapping - 10
Striped vs. Concatenated Meta
Usually, striped meta volumes will perform better than concatenated
ones
– Because they reside on more spindles.
– If there are not enough drives for all the meta members to be on separate
drives consider concatenated.
– If host striping is planned, concatenated meta volumes may be better
Concatenated Meta Volumes can be placed on the same RAID
group
– Can create a reasonable emulation of a native large volume on Symmetrix
DMX systems or Symmetrix V-Max systems
Don’t place striped meta volumes on the same RAID group
(wrapped)
For Virtual Provisioning environments, concatenated meta volumes
work better
– (Thin Meta Volumes)
Striped meta volumes perform better than concatenated meta volumes when there are enough spindles
to support them. However, if the striping leads to the same physical spindle hosting two or more
members of the meta volume, striping loses its effectiveness. In such a case, using concatenated meta
volumes is better.
It is not a good idea to stripe on top of a stripe. Thus, if host striping is planned and meta volumes are
being used, concatenated meta volumes are better.
In Virtual Provisioning environments it is advisable to use concatenated metavolumes"
Hope this helps!
Dumb question - whether it is a striped or concatenated thin device, they spread all over the array with FAST VP policy in place. correct? Why should i think of a thin device as a regular thick device striping on just one RAID group of 4 or 8 disks?
Delete