ClusterFunk

Today I have been working on the design documentation for an HP EVA8100. Its a couple of years since I last worked with EVAs and as a result I have remember how different they are to other SAN storage controllers when it comes to configuration. The following is a list of things to consider when deploying EVAs.

Disk Layout

When specifying you containers HP recommends that disks are added in multiples of 8 disks. This is the optimum for disk write I/O.  A general rule of thumb is the more spindles the better. Specific application requirements need to be considered  e.g. if you intend to backup D2D then it is recommended to have separate containers for data and backups.

Containers

This is the raw “space” that is created when a number of disks is joined together. It is considered best practice to only provision one type of LUN configuration per container e.g. have a container for VRAID5 and a container for VRAID1.  

Sparing
Unlike a traditional RAID array EVA containers span the data across all disk that have been specified for that container. E.g. I have picked 56 spindles for SQL DB LUNS all VRAID1. The sparing level is the number of spindles set aside in the event of disk failure. Depending on the nature of the data stored a sparring Level of 1 or 2 is quite normal.   

V-RAID
EVAs provide three virtual RAID formats RAID 0, RAID 1 and RAID 5. As you would expect the actual capacity available in a container is dependent on the RAID configuration of the LUN created in that container. You can follow the normal sizing e.g. RAID 1 will provide usable capacity that is half  the raw capacity presented for the creation of the LUN 

Levelling
This is the process that is required to distribute the data across all of the spindles in a container. In the event of a failed disk levelling is conducted to redistribute the data onto the sparing disk and also when the replacement is fitted. During levelling operations the overall EVA performance for that container is reduced. 

Occupancy
In order to accommodate the  levelling activity it is not possible to utilise all of the available RAW capacity of a container. The maximum capacity for a container is 95% full. This allows for 5% headroom required to move data around on the spindles. A more practice Occupancy is 90% this allows for faster levelling in the event of failure. 

Zoning
Zoning is the mechanism for isolating SCSI communication on a SAN fabric so that there is a one to one relationship between a host and LUN on the storage controller. This is similar to VLANs in a Ethernet network. Zoning prevents controller/host SCSI traffic from been received by the wrong hosts. It also adds a layer of security by preventing accidental or deliberate attempts to gain access to a LUN from a host other than the intended one. Zoning is implemented via an ACL on a port based on the WWN of a specific remote port. e.g. Port 1 on a switch will only accept traffic from the port with a WWN value of X and will only send traffic from that port to another designated port / WWN.

A zone would normal consist of the

host HBA port/s WWNs
Switch port WWNs (that the host plugs into)
Switch port WWNs (that the storage plugs into)
Storage Controller WWNs
Plus possibly the WWNs of ports associated with backups such as SAN presented tape library

LUN Masking
Similar to Zoning, LUN Masking is the mechanism employed by the storage controller to present a LUN to a specific host. Once a LUN has been created a LUN mask is assigned that mean the storage controller will ignore all operations against that LUN apart from one that come from the designated host or hosts. In a Windows Cluster a LUN has multiple hosts in its LUN mask to enable the LUN to be accessed by the cluster nodes as required. 

MPIO – Microsoft Multipath I/O

MPIO is the Microsoft software that provided multipath management in SANs that employ redundant paths from the host to the storage.

I have previously worked on EVA5000s, 6000s and 8000s.  The last time I worked on the 5000 series the MPIO feature set was limited to simple path management in other words the full feature DSM was not available for the 3000 and 5000 series. However since then the Full Feature DSM has been made available which supports full HBA load balancing as well as multipath management. The only point to consider is that the EVA VCS (firmware) revision is 4.xxx  

Useful Links

HP EVA 4000/6000/8000  Configuration Best Practice
http://h71028.www7.hp.com/ERC/downloads/4AA0-2787ENW.pdf

HP StorageWorks SAN
SAN Visibility tool and StorageWorks SAN Designer

XP Version
http://h20000.www2.hp.com/bizsupport/TechSupport/Software…..

Other OS Options
Here