74 lines
4.3 KiB
HTML
74 lines
4.3 KiB
HTML
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<meta name="DC.Title" content="How mirrored protection works" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>How mirrored protection works</title>
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</head>
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<body id="hdrmirrorwork"><a name="hdrmirrorwork"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">How mirrored protection works</h1>
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<div><p>Because mirrored protection is configured by disk pool, you can mirror
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one, some, or all disk pools on the system. By default, every system has a
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system disk pool. It is not necessary to create user disk pools in order to
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use mirrored protection. Although mirrored protection is configured by disk
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pool, all disk pools must be mirrored to provide for maximum system availability.
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If a disk unit fails in a disk pool that is not mirrored, the system cannot
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be used until the disk unit is repaired or replaced.</p>
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<p>The start mirrored pairing algorithm automatically selects a mirrored configuration
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that provides the maximum protection at the bus, I/O (input/output) processor,
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or I/O adapter for the hardware configuration of the system. When storage
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units of a mirrored pair are on separate buses, they have maximum independence
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or protection. Because they do not share any resource at the bus, I/O processor,
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or I/O adapter levels, a failure in one of these hardware components allows
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the other mirrored unit to continue operating.</p>
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<p>Any data that is written to a unit that is mirrored is written to both
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storage units of the mirrored pair. When data is read from a unit that is
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mirrored, the read operation can be from either storage unit of the mirrored
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pair. It is transparent to the user which mirrored unit the data is being
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read from. A user is not aware of the existence of two physical copies of
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the data.</p>
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<p>If one storage unit of a mirrored pair fails, the system suspends mirrored
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protection to the failed mirrored unit. The system continues to operate using
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the remaining mirrored unit. The failing mirrored unit can be
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physically repaired or replaced.</p>
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<p>After the failed mirrored unit is repaired or replaced, the system synchronizes
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the mirrored pair by copying current data from the storage unit that has remained
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operational to the other storage unit. During synchronization, the mirrored
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unit to which the information is being copied is in the resuming state. Synchronization
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does not require a dedicated system and runs concurrently with other jobs
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on the system. System performance is affected during synchronization. When
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synchronization is complete, the mirrored unit becomes active.</p>
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<p>For details on storage on your server, see <a href="rzalystordet.htm">Disk storage concepts</a>.</p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzalycmaintdef.htm">Concurrent maintenance</a></strong><br />
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</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalydpconcepts.htm">Disk protection</a></div>
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</div>
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</div>
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</body>
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