HP AutoRAID 12H manual System, Administrator’s dilemma, Adding capacity with, Hp virtual arrays

section 1				hp storage white paper
the system				• determining the number of disks required
administrator’s dilemma				for the necessary performance
				• creating the LUNs—note: creating LUNs
Change is the issue. Many environments change				takes only a few seconds per LUN1
over time and this makes their initial configurations
progressively less and less optimal. The dilemma				Step away from the array; the configuration is
is that an optimum configuration today eventually				now complete. Every other step is automatic.
becomes out-of-date, and typically over time,				RAID levels are automatic. The different capacity,
performance degrades in traditional arrays, but				number, and speeds of disk drives are automatically
the administrator usually has neither the time nor				accounted for. The cache page size is automatically
the window of opportunity to bring the system				set. Even the disk formatting is performed
down and perform the necessary reconfiguration.				automatically. Moreover, after the LUNs are set,
Access patterns change. Different areas of the				the array is immediately available to accept data.
				The array does the work, not the administrator.
database become more highly used. Sometimes
at the end of the month certain data that normally				Not only is this the initial configuration process,
lies unused now becomes highly used and requires				but the process is just as simple for any subsequent
higher performance. All of this poses problems				reconfigurations. In other words, if LUNs have to
for the conscientious system administrator.				be deleted and new ones created, the process is
At first, the administrator notices a change in				just as simple. Note: As with any array, if you
				wanted to delete the LUNs but save the data,
performance, but it is not enough to justify bringing				you would have to do a backup and restore.
the system down. However, over time, the
performance continues to degrade until eventually				adding capacity with
the problem is so severe that the administrator is				hp virtual arrays
forced to bring the system down over the protests
of the users. He must then go through all 13				HP’s Virtual Array Architecture also simplifies the
configuration steps, including		binding all	the
				process of adding capacity to an array. Today,
LUNs and waiting for the reformat to complete.
				many traditional arrays allow the administrator
After that the cycle begins again: Performance
				to add disks on-the-fly—in other words, to add a
initially is great,	but over time it degrades
				disk drive when the array is up and running and
until finally the pain increases to the point that
a reconfiguration again becomes justifiable.				accepting I/Os.
managing the hp virtual array				However, when the disk drive is added to a
Configuring an HP Virtual Array is much simpler				traditional array, it is not part of any LUN. It is
				not formatted, and it is not able to accept data.
than the process for configuring a traditional				An administrator must go in and manually perform
array. Remember the complex steps involved in				those functions. If the disk drive is to be added
configuring a traditional array? The steps involved
				to an already existing RAID group, then the data
in configuring the HP Virtual Array consist of:
				in that group must first be backed-up and later
• determining	the total	capacity	and	restored to the newly created LUN that now
performance requirements				contains the new disk drive. And except for the
• for each application,		determining	the	backup, the steps are the same as when an
number and size of LUNs				array is first configured.

1.4