Solaris 11.4 meta devices for DDT

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FII

New Member
Apr 10, 2019
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Hi,
I have some questions:
In 11.4 man zpool says this :
" meta
A device used to optimize reads of certain types of ZFS metadata,
in particular, deduplication entries. If more than one meta device
is specified, operations will be load balanced between them. Meta
devices can be mirrored. However, raidz vdev types are not sup-
ported. For more information, see the "Meta Devices" section.
"
and this:
"
Meta Devices
Devices can be added to a storage pool as meta devices. These devices
store copies of critical metadata which needs to be accessed in a non-
sequential manner. This functionality is especially useful for dedupli-
cation entries. Since copies of the metadata are also written to the
main storage pool, I/O errors to this device can be recovered and this
device does not have to be mirrored.
To create a pool with meta devices, specify a meta vdev with any number
of devices. For example:
# zpool create pool c0d0 c1d0 meta c2d0 c3d0
Multiple meta devices can be specified, and they can be mirrored, but
they cannot be part of a raidz configuration.
Meta devices can be added, replaced, attached, detached, imported, and
exported as part of the larger pool.
"
1.Where can I find more info/docs about meta devices ?
2. Should I use (1 or 2) NVME flash or optane 16GB for 100GB deduplication table ?
3. With meta devices the ARC ram will held only pointers to DDT entries ?
4. Is it worth it ?

I guess meta will see mostly read activity , so a flash won't have that much wear .
Pool will have 20~30 zvols, thin provisioned VM's and hopefully deduplicated.
Any advice ?


Please forgive mistakes , english is not my native language.

Thank You,
FI