IBM System Storage DS4000, Руководство по оборудованию

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IBM Midrange System Storage Hardware Guide
Heterogeneous hosts
When implementing a DS5000 storage subsystem solution, a mixture of host servers with
different operating systems can be used (clustered and non-clustered variants of the same
operating systems). However, all logical drives in a single storage partition must be
configured for the same operating system. Also, all hosts in that same storage partition must
run the same defined operating system.
Access logical drive
The DS5000 storage subsystem will automatically create a LUN 31 for each host attached.
This is used for in-band management, so if you do not plan to manage the DS5000 storage
subsystem from that host, you can delete LUN 31, which will give you one more LUN to use
per host.
You can always recreate it if later you decide to use in-band management.
4.1.5 Segment size
A segment, in a logical drive, is the amount of data, in kilobytes, that the controller writes on a
single physical drive before writing data on the next physical drive. Depending on your data
structure, you can optimize the creation of your logical drives for this value.
When you create a logical drive, the default segment size choose is 128 KB, unless you are
creating logical drives under a RAID 3, or choosing the multimedia type for the logical drive, in
which case a segment size of 256 KB is used.
The choice of a segment size can have a major influence on performance in both IOPS and
throughput. You can choose the defaults, which is a good choice for general usage, or
consider the following to properly select a the logical drive segment size customized for your
needs:
򐂰 The characteristics of your application, IOPS demanding, or Throughput demanding,
whether random or sequential.
򐂰
The I/O block size of the host that will use the logical drive.
– Small IO sizes allow for greater transaction (IOPS) rates.
– Large IO sizes allows a better transfer rate in MBps.
򐂰 The RAID protection and number of disk drives that are participating in the logical drive
array.
To calculate the best segment size in this environment, consider the RAID protection and
number of drives participating in the array.
Segment Size > I/O block size request
This is the best option for high IOPs and random requests.
򐂰 Several transactions are satisfied in a single operation to a disk.
򐂰 There is higher IOPS.
򐂰 It is ideal for random I/O requests, such as the database file system.
򐂰 The best option is start with Segment size >= 2 x Block Size for high IOPS.
Important: Heterogeneous hosts are only supported with storage partitioning enabled.