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zhangyue
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Reviewed-by: Miskanin, Jan <jan.miskanin@t-systems.com> Co-authored-by: zhangyue <zhangyue164@huawei.com> Co-committed-by: zhangyue <zhangyue164@huawei.com>
194 lines
18 KiB
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194 lines
18 KiB
HTML
<a name="evs_01_0085"></a><a name="evs_01_0085"></a>
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<h1 class="topictitle1">Constraints</h1>
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<div id="body1557390262095"><p id="evs_01_0085__p8060118">This section describes the constraints on using EVS.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" id="evs_01_0085__table1118143194610" frame="border" border="1" rules="all"><caption><b>Table 1 </b>Constraints on using EVS</caption><thead align="left"><tr id="evs_01_0085__row211818374618"><th align="left" class="cellrowborder" valign="top" width="19.24%" id="mcps1.3.2.2.4.1.1"><p id="evs_01_0085__p10904645144718">Scenario</p>
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</th>
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<th align="left" class="cellrowborder" valign="top" width="28.439999999999998%" id="mcps1.3.2.2.4.1.2"><p id="evs_01_0085__p811811314469">Item</p>
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</th>
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<th align="left" class="cellrowborder" valign="top" width="52.32%" id="mcps1.3.2.2.4.1.3"><p id="evs_01_0085__p2011815314465">Restrictions</p>
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</th>
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</tr>
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</thead>
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<tbody><tr id="evs_01_0085__row17878243125712"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p18881412405">Capacity of a data disk</p>
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</td>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul10881161211016"><li id="evs_01_0085__li10881181217012">High I/O: 10 GiB to 32,768 GiB</li><li id="evs_01_0085__li19881171211011">General Purpose SSD: 10 GiB to 32,768 GiB</li><li id="evs_01_0085__li1688117121804">Ultra-high I/O: 10 GiB to 32,768 GiB</li><li id="evs_01_0085__li138814124010">Extreme SSD: 10 GiB to 32,768 GiB</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row1680895385915"><td class="cellrowborder" rowspan="5" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p080805385918">Disk performance</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p1528119364138">Common I/O</p>
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</td>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><ul id="evs_01_0085__ul11281173621310"><li id="evs_01_0085__li1428193631316">Maximum IOPS per disk: 1,000</li><li id="evs_01_0085__li192813367138">Maximum throughput per disk: 90 MiB/s</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row780955365911"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p9281203661312">High I/O</p>
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</td>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul4281173620131"><li id="evs_01_0085__li11282123611313">Maximum IOPS per disk: 3,000</li><li id="evs_01_0085__li628203661312">Maximum throughput per disk: 150 MiB/s</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row7479153810108"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p16480938131013">General Purpose SSD</p>
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</td>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul130115544100"><li id="evs_01_0085__li19301154101017">Maximum IOPS per disk: 20,000</li><li id="evs_01_0085__li8302125415106">Maximum throughput per disk: 250 MiB/s</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row3809185355918"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p1428223671320">Ultra-high I/O</p>
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</td>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul32821536191317"><li id="evs_01_0085__li628213363138">Maximum IOPS per disk: 20,000</li><li id="evs_01_0085__li128223616137">Maximum throughput per disk: 350 MiB/s</li></ul>
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</tr>
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<tr id="evs_01_0085__row881085375911"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p1028319364133">Extreme SSD</p>
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</td>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul22842369133"><li id="evs_01_0085__li16284163620131">Maximum IOPS per disk: 128,000</li><li id="evs_01_0085__li11284536191320">Maximum throughput per disk: 1,000 MiB/s</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row172261548165314"><td class="cellrowborder" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p42277480533">Disk creation restrictions on accounts</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p562051810226">Permission requirement</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p165653162311">The account used to create EVS disks must have the evs:volumes:create permission. For how to add permissions, see <a href="evs_01_0090.html">EVS Custom Policies</a>.</p>
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</td>
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</tr>
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<tr id="evs_01_0085__row191181936469"><td class="cellrowborder" rowspan="7" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p1904114513475">Disk creation</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p111187374613">Maximum number of disks that can be created at a time</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p171187374614">100</p>
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</tr>
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<tr id="evs_01_0085__row152110581554"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p8211125814515">Disk creation from snapshot</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul127916354812"><li id="evs_01_0085__li8280133194810">The disk type of the new disk is the same as that of the snapshot's source disk.</li><li id="evs_01_0085__li1328016314484">The device type of the new disk is the same as that of the snapshot's source disk.</li><li id="evs_01_0085__li1928019319482">The encryption attribute of the new disk is the same as that of the snapshot's source disk.</li><li id="evs_01_0085__li10280535481">Batch creation is not supported. One can create only one disk from a snapshot at a time.</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row491142217714"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p49111222170">Disk creation from backup</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul043616974815"><li id="evs_01_0085__li543689204815">Batch creation is not supported. One can create only one disk from a backup at a time.</li><li id="evs_01_0085__li154376924817">One backup cannot be used for concurrent disk creation operations at the same time. For example, if you are creating disk A from a backup, this backup can be used to create another disk only after disk A has been created.</li><li id="evs_01_0085__li8437793480">If a disk is created from a backup of a system disk, the new disk can be used as a data disk only.</li></ul>
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</td>
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<tr id="evs_01_0085__row0730102918105"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p19730929111017">Disk creation from image</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul16532028273"><li id="evs_01_0085__li453310289720">The device type of the new disk is the same as that of the image's source disk.</li><li id="evs_01_0085__li14533528273">The encryption attribute of the new disk is the same as that of the image's source disk.</li></ul>
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</td>
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</tr>
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<tr id="evs_01_0085__row182021616113010"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p4204171617305">Device type</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p52045166303">The device type of a disk cannot be changed after the disk has been created.</p>
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</td>
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</tr>
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<tr id="evs_01_0085__row1561941811306"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p1461931819309">Disk sharing</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p262031811308">The sharing attribute of a disk cannot be changed after the disk has been created.</p>
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<tr id="evs_01_0085__row57211727121"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p1272114281214">Disk encryption</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p172113217123">The encryption attribute of a disk cannot be changed after the disk has been created.</p>
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</td>
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<tr id="evs_01_0085__row3661181015335"><td class="cellrowborder" rowspan="6" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p753043615516">Disk attachment</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p20530103612519">Constraints on region and AZ</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p1353015368512">The disk and <span id="evs_01_0085__text2056151454">server</span> must be in the same region and AZ.</p>
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</td>
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<tr id="evs_01_0085__row10782151800"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p4208258509">Maximum number of <span id="evs_01_0085__text83587221151">server</span>s that a non-shared disk can be attached to</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p92081158203">1</p>
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</td>
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<tr id="evs_01_0085__row566118108336"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p103896427151">Maximum number of <span id="evs_01_0085__text2038904213154">server</span>s that a shared disk can be attached to</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p320034814519">16</p>
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</td>
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<tr id="evs_01_0085__row1342215481586"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p4361610154015">Maximum number of disks that can be attached to an ECS</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p189318711436">This value varies with ECS types.</p>
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<p id="evs_01_0085__p199621239810">For details, see section "Can I Attach Multiple Disks to an ECS?" in the <em id="evs_01_0085__i13117114244311">Elastic Cloud Server User Guide</em>.</p>
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<tr id="evs_01_0085__row916192783610"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p141611527123611">Maximum number of disks that can be attached to a BMS</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p1916111272363">60 (1 system disk and 59 data disks)</p>
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</td>
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<tr id="evs_01_0085__row12887755892"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p488720551890">Device name</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul671933211016"><li id="evs_01_0085__li14719183241014">System disk: /dev/vda, /dev/sda, and /dev/xvda</li><li id="evs_01_0085__li24994671019">Data disk: /dev/vd[b-z], /dev/sd[b-z], and /dev/xvd[b-z]</li></ul>
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<tr id="evs_01_0085__row1134012983313"><td class="cellrowborder" rowspan="4" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p375417415182">Disk capacity expansion</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p275454191815">Capacity expansion</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p375464151816">Disk capacity can be expanded, but cannot be reduced.</p>
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<tr id="evs_01_0085__row17340102918335"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p28171852171918">Capacity expansion of non-shared disks</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p1181785291910">Some <span id="evs_01_0085__text12132145852119">server</span> OSs support the capacity expansion of non-shared, In-use disks.</p>
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<p id="evs_01_0085__p173765020618">For details, see <a href="evs_01_0007.html">Expanding Capacity for an In-use EVS Disk</a>.</p>
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<tr id="evs_01_0085__row634110296335"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p18784173181912">Capacity expansion of shared disks</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p10784163131911">A shared disk must be detached from all its <span id="evs_01_0085__text1187140112214">server</span>s before expansion. That is, the shared disk status must be <strong id="evs_01_0085__b274717563558">Available</strong>.</p>
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<tr id="evs_01_0085__row3341162923316"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p058797132414">Expansion increment</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p2587117132417">1 GiB</p>
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<tr id="evs_01_0085__row19579573333"><td class="cellrowborder" rowspan="2" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p108514511156">Disk detachment</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p108519519513">System disk detachment</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p68555117513">A system disk can only be detached offline, which means that the server must be in the <strong id="evs_01_0085__b10499218195615">Stopped</strong> state.</p>
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<tr id="evs_01_0085__row125765793310"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p1987182441613">Data disk detachment</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p9987122431619">A data disk can be detached online or offline, that is, its <span id="evs_01_0085__text23046719185824">server</span> can either be in the <strong id="evs_01_0085__b14334787587">Running</strong> or <strong id="evs_01_0085__b18383111115815">Stopped</strong> state.</p>
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<tr id="evs_01_0085__row928514256512"><td class="cellrowborder" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p5286162520512">Disk deletion</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p1286182515112">Deletion of disks</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><ul id="evs_01_0085__ul28721941432"><li id="evs_01_0085__evs_01_0005_li124211110334">The disk status is <strong id="evs_01_0085__evs_01_0005_b985812257218">Available</strong>, <strong id="evs_01_0085__evs_01_0005_b7859625162117">Error</strong>, <strong id="evs_01_0085__evs_01_0005_b148613253213">Expansion failed</strong>, <strong id="evs_01_0085__evs_01_0005_b168621925102111">Restoration failed</strong>, or <strong id="evs_01_0085__evs_01_0005_b3862132512215">Rollback failed</strong>.</li><li id="evs_01_0085__evs_01_0005_li107325132152">The disk is not locked by any service.</li><li id="evs_01_0085__evs_01_0005_li18424153316">The shared disk has been detached from all its <span id="evs_01_0085__evs_01_0005_text123837584211">servers</span>.</li></ul>
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<tr id="evs_01_0085__row189401630142517"><td class="cellrowborder" rowspan="2" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p59401130182516">Snapshot</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p99401230142512">Maximum number of snapshots that can be created for a disk</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p19940630162514">7</p>
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<tr id="evs_01_0085__row10837038203710"><td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p208371538133716">Snapshot data rollback to disk</p>
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<td class="cellrowborder" valign="top" headers="mcps1.3.2.2.4.1.2 "><ul id="evs_01_0085__ul19157191192511"><li id="evs_01_0085__evs_01_0012_li88311154183410">Data of a snapshot can be rolled back only to its source disk. Rollback to another disk is not possible.</li><li id="evs_01_0085__evs_01_0012_li283115473420">Data of a snapshot can be rolled back only when the snapshot status is <strong id="evs_01_0085__evs_01_0012_b65201938121320">Available</strong> and its source disk status is <strong id="evs_01_0085__evs_01_0012_b1521038111311">Available</strong> (not attached to any <span id="evs_01_0085__evs_01_0012_text683113548347">server</span>) or <strong id="evs_01_0085__evs_01_0012_b6522838191311">Rollback failed</strong>. If the source disk is attached, detach the disk first.</li><li id="evs_01_0085__evs_01_0012_li283125419345">A snapshot whose name starts with <strong id="evs_01_0085__evs_01_0012_b540317103414">autobk_snapshot_vbs_</strong>, <strong id="evs_01_0085__evs_01_0012_b1941097143415">manualbk_snapshot_vbs_</strong>, <strong id="evs_01_0085__evs_01_0012_b1441016773416">autobk_snapshot_csbs_</strong>, or <strong id="evs_01_0085__evs_01_0012_b184107753418">manualbk_snapshot_csbs_</strong> is automatically generated during backup. Such a snapshot can only be viewed. It cannot be used to roll back the disk data.</li><li id="evs_01_0085__evs_01_0012_li11562183031614">Spot instances do not support snapshot-based rollback of the disk data.</li></ul>
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<tr id="evs_01_0085__row21182344614"><td class="cellrowborder" valign="top" width="19.24%" headers="mcps1.3.2.2.4.1.1 "><p id="evs_01_0085__p7904104594715">Tag</p>
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<td class="cellrowborder" valign="top" width="28.439999999999998%" headers="mcps1.3.2.2.4.1.2 "><p id="evs_01_0085__p21187318463">Maximum number of tags that can be added for a disk</p>
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<td class="cellrowborder" valign="top" width="52.32%" headers="mcps1.3.2.2.4.1.3 "><p id="evs_01_0085__p11182036469">10</p>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="evs_01_0119.html">Overview</a></div>
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</div>
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</div>
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