On Mar 25, 2012, at 8:58 PM, Yuri Vorobyev wrote:

> Hello.
> What the best practices for choosing ZFS volume volblocksize setting for 
> VMware VMFS-5?
> VMFS-5 block size is 1Mb. Not sure how it corresponds with ZFS.

Zero correlation. 

What I see on the wire from VMFS is 16KB random reads followed by 4KB random 
VMFS reads the same set of 16KB data again and again, so it tends to get nicely 
in the MFU portion of the ARC.

> Setup details follow:
> - 11 pairs of mirrors;
> - 600Gb 15k SAS disks;
> - SSDs for L2ARC and ZIL
> - COMSTAR FC target;
> - about 30 virtual machines, mostly Windows (so underlying file systems is 
> NTFS with 4k block)
> - 3 ESXi hosts.
> Also, i will glad to hear volume layout suggestions.
> I see several options:
> - one big zvol with size equal size of the pool;
> - one big zvol with size of the pool-20% (to avoid fragmentation);

A zvol with reservation is one way of implemented the reservations often seen in
other file systems.

> - several zvols (size?).

In general, for COMSTAR, more LUs is better.
 -- richard

DTrace Conference, April 3, 2012, 
ZFS Performance and Training

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