HP VMA-series Memory Arrays Aviso descarregar pdf (Página 13)

VMA SAN Gateway: general recommendations and

limitations

The following are general recommendations for getting optimal performance with the HP VMA SAN

Gateway and connected HP VMA-series Memory Arrays.

Alignment of data transfer I/O block sizes

The internal flash addressing of the VMA is based on 4K (4096) byte boundaries. Read or write

requests that do not begin on a 4KB aligned target block address or are of I/O sizes not a multiple of

4KB might suffer a performance impact. Write performance is more seriously affected by non-4KB

alignment. For example, if a user application writes 512 bytes starting at the last 256 bytes of a 4K

page, the result on hardware would be two 4K read-modify-write updates.

In order to achieve optimal throughput and performance with the VMA-series Memory Arrays, care

should be given to tuning the intended application, data layout structures on the array, and the

connected host server.

Data layout structure alignment on VMA Array LUNs

The data layout structures created on the VMA LUNs by a logical volume manager and file system on

the host should be made so that they are 4KB aligned, meaning that partition sizes, LVM striping and

other data structures are 4KB aligned. Consider the following when creating data layout structures on

the VMA:

 Partition sizes are 4KB aligned

 Volume manager stripe sizes are multiple of 4KB

 File system blocks are 4KB aligned

Tune application to issue I/Os which are multiple of 4KB

Most high level applications can be configured to issue certain I/O block sizes for increased

performance. Ensure that configured I/O block size and if appropriate the beginning block

addresses for I/Os are 4KB aligned.

Create multiple LUNs for parallelization of I/O for applications

Creating multiple LUNs on the connected VMA arrays might allow applications to launch multiple

threads for greater I/O parallelism and performance. It is currently recommended to configure no

more than 32 LUNs with this initial release of the VMA SAN Gateway.

LUN 0 of the VMA SAN Gateway

LUN 0 is considered a reserved device and various issues can occur if LUN 0 is not accessible by all

connected host servers. Thus, the VMA SAN Gateway will prompt for configured LUNs to begin with

LUN ID #1. If a specific operating system requires configuration of a LUN ID #0, this can be done by

explicitly entering „0‟ for the LUN ID when creating a LUN. However, any configuration changes or

accessibility change to an explicitly created LUN ID #0 might cause disruption of service including

inability to discover and access LUNs and stored data to other connected server hosts.

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HP VMA-series Memory Arrays Aviso Página 13