Oracle ZFS Storage Appliance: How to avoid misalignment when using ASM on Solaris clients

Asset ID:	1-71-2036559.1
Update Date:	2018-01-05
Keywords:

Solution Type Technical Instruction Sure

Solution 2036559.1 : Oracle ZFS Storage Appliance: How to avoid misalignment when using ASM on Solaris clients

Applies to:

Sun ZFS Storage 7120 - Version All Versions to All Versions [Release All Releases]
Sun ZFS Storage 7320 - Version All Versions to All Versions [Release All Releases]
Oracle ZFS Storage ZS3-2 - Version All Versions to All Versions [Release All Releases]
Oracle ZFS Storage ZS3-4 - Version All Versions to All Versions [Release All Releases]
Oracle ZFS Storage ZS3-BA - Version All Versions to All Versions [Release All Releases]
7000 Appliance OS (Fishworks)

Goal

From the different ASM documentation available in the web, misalignment issues are not emphasized enough.
One can even find this :
Each disk is formatted and a partition is created starting from 1 cylinder.
The available disks can be seen using the format command as shown below […]

partition> print
Current partition table (unnamed):
Total disk cylinders available: 1302 + 2 (reserved cylinders)
Part Tag        Flag Cylinders Size   Blocks
0    unassigned wm   1 – 1299 9.95GB (1299/0/0) 20868435
1    unassigned wm   0         0      (0/0/0) 0
2    backup     wu   0 – 1301 9.97GB (1302/0/0) 20916630
3    unassigned wm   0         0      (0/0/0) 0
4    unassigned wm   0         0      (0/0/0) 0
5    unassigned wm   0         0      (0/0/0) 0
6    unassigned wm   0         0      (0/0/0) 0
7    unassigned wm   0         0      (0/0/0) 0
8    boot       wu   0 – 0     7.84MB (1/0/0) 16065
9    unassigned wm   0         0      (0/0/0) 0

partition> label

Using cylinder 1 of slice0 will clearly lead to miss-alignments and extra IOs, as described here :
http://blogs.oracle.com/dlutz/entry/partition_alignment_guidelines_for_unified

Solution

To avoid the miss-alignment, we need to follow the following document when assigning the LUNs to the ASM layer :
http://www.oracle.com/technetwork/server-storage/sun-unified-storage/documentation/partitionalign-111512-1875560.pdf

See page 28 :
Recommendations for Oracle Solaris Clients
If possible, use EFI-type labels for data disks. When manually labeling the disks/LUNs with the format -e command, correct the start sector of at least 256. This guarantees alignment with the underlying block structure of a Sun ZFS Storage Appliance LUN for block sizes up to 128KB. Use a start sector value of 2048 (1MB), the current accepted industry standard for space offset used when partitioning a disk/LUN. When a SMI-type disk label is required on an Oracle Solaris x86 client, create one slice that holds the whole Oracle Solaris root file system. For that slice start cylinder, use the following formula to find the correct start cylinder value:

(cylinder number * sectors/cylinder * sector size) % LUN blocksize == 0

In short, when using a disk slice for ASM with an EFI label, make sure the first sector is 256 for LUNs created with a volblocksize of 128K on the ZFS appliance or 2048 for LUNs created with a volblocksize of 1MB.

Here is a 'format' command output from a Solaris host using a LUN (set with an EFI label) exported by a ZFS appliance :

SolarisHost # format
[..]
selecting c0t600144F09DFB2E93000055A7D0DF0016d0
[disk formatted]

partition> print
Current partition table (original):
Total disk sectors available: 419413949 + 16384 (reserved sectors)

Part      Tag    Flag     First Sector         Size         Last Sector
    0        usr    wm               256      199.99GB          419413981
    1 unassigned    wm                 0           0               0
    2 unassigned    wm                 0           0               0
    3 unassigned    wm                 0           0               0
    4 unassigned    wm                 0           0               0
    5 unassigned    wm                 0           0               0
    6 unassigned    wm                 0           0               0
    8   reserved    wm         419413983        8.00MB          419430366

References

<NOTE:1213714.1> - Sun ZFS Storage Appliance: Performance clues and considerations

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