1328 .Sy most ,
1329 ZFS stores an extra copy of most types of metadata.
1330 This can improve performance of random writes, because less metadata must be
1331 written.
1332 In practice, at worst about 100 blocks
1333 .Po of
1334 .Sy recordsize
1335 bytes each
1336 .Pc
1337 of user data can be lost if a single on-disk block is corrupt.
1338 The exact behavior of which metadata blocks are stored redundantly may change in
1339 future releases.
1340 .Pp
1341 The default value is
1342 .Sy all .
1343 .It Sy refquota Ns = Ns Em size Ns | Ns Sy none
1344 Limits the amount of space a dataset can consume.
1345 This property enforces a hard limit on the amount of space used.
1346 This hard limit does not include space used by descendents, including file
1347 systems and snapshots.
1348 .It Sy refreservation Ns = Ns Em size Ns | Ns Sy none
1349 The minimum amount of space guaranteed to a dataset, not including its
1350 descendents.
1351 When the amount of space used is below this value, the dataset is treated as if
1352 it were taking up the amount of space specified by
1353 .Sy refreservation .
1354 The
1355 .Sy refreservation
1356 reservation is accounted for in the parent datasets' space used, and counts
1357 against the parent datasets' quotas and reservations.
1358 .Pp
1359 If
1360 .Sy refreservation
1361 is set, a snapshot is only allowed if there is enough free pool space outside of
1362 this reservation to accommodate the current number of
1363 .Qq referenced
1364 bytes in the dataset.
1365 .Pp















1366 This property can also be referred to by its shortened column name,
1367 .Sy refreserv .
1368 .It Sy reservation Ns = Ns Em size Ns | Ns Sy none
1369 The minimum amount of space guaranteed to a dataset and its descendants.
1370 When the amount of space used is below this value, the dataset is treated as if
1371 it were taking up the amount of space specified by its reservation.
1372 Reservations are accounted for in the parent datasets' space used, and count
1373 against the parent datasets' quotas and reservations.
1374 .Pp










1375 This property can also be referred to by its shortened column name,
1376 .Sy reserv .
1377 .It Sy secondarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
1378 Controls what is cached in the secondary cache
1379 .Pq L2ARC .
1380 If this property is set to
1381 .Sy all ,
1382 then both user data and metadata is cached.
1383 If this property is set to
1384 .Sy none ,
1385 then neither user data nor metadata is cached.
1386 If this property is set to
1387 .Sy metadata ,
1388 then only metadata is cached.
1389 The default value is
1390 .Sy all .
1391 .It Sy setuid Ns = Ns Sy on Ns | Ns Sy off
1392 Controls whether the setuid bit is respected for the file system.
1393 The default value is
1394 .Sy on .

1569 The reservation is kept equal to the volume's logical size to prevent unexpected
1570 behavior for consumers.
1571 Without the reservation, the volume could run out of space, resulting in
1572 undefined behavior or data corruption, depending on how the volume is used.
1573 These effects can also occur when the volume size is changed while it is in use
1574 .Pq particularly when shrinking the size .
1575 Extreme care should be used when adjusting the volume size.
1576 .Pp
1577 Though not recommended, a
1578 .Qq sparse volume
1579 .Po also known as
1580 .Qq thin provisioning
1581 .Pc
1582 can be created by specifying the
1583 .Fl s
1584 option to the
1585 .Nm zfs Cm create Fl V
1586 command, or by changing the reservation after the volume has been created.
1587 A
1588 .Qq sparse volume
1589 is a volume where the reservation is less then the volume size.

1590 Consequently, writes to a sparse volume can fail with
1591 .Er ENOSPC
1592 when the pool is low on space.
1593 For a sparse volume, changes to
1594 .Sy volsize
1595 are not reflected in the reservation.





1596 .It Sy vscan Ns = Ns Sy on Ns | Ns Sy off
1597 Controls whether regular files should be scanned for viruses when a file is
1598 opened and closed.
1599 In addition to enabling this property, the virus scan service must also be
1600 enabled for virus scanning to occur.
1601 The default value is
1602 .Sy off .
1603 .It Sy xattr Ns = Ns Sy on Ns | Ns Sy off
1604 Controls whether extended attributes are enabled for this file system.
1605 The default value is
1606 .Sy on .
1607 .It Sy zoned Ns = Ns Sy on Ns | Ns Sy off
1608 Controls whether the dataset is managed from a non-global zone.
1609 See the
1610 .Sx Zones
1611 section for more information.
1612 The default value is
1613 .Sy off .
1614 .El
1615 .Pp

1328 .Sy most ,
1329 ZFS stores an extra copy of most types of metadata.
1330 This can improve performance of random writes, because less metadata must be
1331 written.
1332 In practice, at worst about 100 blocks
1333 .Po of
1334 .Sy recordsize
1335 bytes each
1336 .Pc
1337 of user data can be lost if a single on-disk block is corrupt.
1338 The exact behavior of which metadata blocks are stored redundantly may change in
1339 future releases.
1340 .Pp
1341 The default value is
1342 .Sy all .
1343 .It Sy refquota Ns = Ns Em size Ns | Ns Sy none
1344 Limits the amount of space a dataset can consume.
1345 This property enforces a hard limit on the amount of space used.
1346 This hard limit does not include space used by descendents, including file
1347 systems and snapshots.
1348 .It Sy refreservation Ns = Ns Em size Ns | Ns Sy none Ns | Ns Sy auto
1349 The minimum amount of space guaranteed to a dataset, not including its
1350 descendents.
1351 When the amount of space used is below this value, the dataset is treated as if
1352 it were taking up the amount of space specified by
1353 .Sy refreservation .
1354 The
1355 .Sy refreservation
1356 reservation is accounted for in the parent datasets' space used, and counts
1357 against the parent datasets' quotas and reservations.
1358 .Pp
1359 If
1360 .Sy refreservation
1361 is set, a snapshot is only allowed if there is enough free pool space outside of
1362 this reservation to accommodate the current number of
1363 .Qq referenced
1364 bytes in the dataset.
1365 .Pp
1366 If
1367 .Sy refreservation
1368 is set to
1369 .Sy auto ,
1370 a volume is made dense
1371 .Po or
1372 .Qq not sparse
1373 .Pc .
1374 .Sy refreservation Ns = Ns Sy auto
1375 is only supported on volumes. See
1376 .Sy volsize
1377 in the
1378 .Sx Native Properties
1379 section for more information about sparse volumes.
1380 .Pp
1381 This property can also be referred to by its shortened column name,
1382 .Sy refreserv .
1383 .It Sy reservation Ns = Ns Em size Ns | Ns Sy none Ns | Ns Sy auto
1384 The minimum amount of space guaranteed to a dataset and its descendants.
1385 When the amount of space used is below this value, the dataset is treated as if
1386 it were taking up the amount of space specified by its reservation.
1387 Reservations are accounted for in the parent datasets' space used, and count
1388 against the parent datasets' quotas and reservations.
1389 .Pp
1390 See
1391 .Sy refreservation Ns = Ns Sy auto
1392 above for a description of the behavior of setting
1393 .Sy reservation
1394 to
1395 .Sy auto .
1396 If the pool is at version 9 or later,
1397 .Sy refreservation Ns = Ns Sy auto
1398 should be used instead.
1399 .Pp
1400 This property can also be referred to by its shortened column name,
1401 .Sy reserv .
1402 .It Sy secondarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
1403 Controls what is cached in the secondary cache
1404 .Pq L2ARC .
1405 If this property is set to
1406 .Sy all ,
1407 then both user data and metadata is cached.
1408 If this property is set to
1409 .Sy none ,
1410 then neither user data nor metadata is cached.
1411 If this property is set to
1412 .Sy metadata ,
1413 then only metadata is cached.
1414 The default value is
1415 .Sy all .
1416 .It Sy setuid Ns = Ns Sy on Ns | Ns Sy off
1417 Controls whether the setuid bit is respected for the file system.
1418 The default value is
1419 .Sy on .

1594 The reservation is kept equal to the volume's logical size to prevent unexpected
1595 behavior for consumers.
1596 Without the reservation, the volume could run out of space, resulting in
1597 undefined behavior or data corruption, depending on how the volume is used.
1598 These effects can also occur when the volume size is changed while it is in use
1599 .Pq particularly when shrinking the size .
1600 Extreme care should be used when adjusting the volume size.
1601 .Pp
1602 Though not recommended, a
1603 .Qq sparse volume
1604 .Po also known as
1605 .Qq thin provisioning
1606 .Pc
1607 can be created by specifying the
1608 .Fl s
1609 option to the
1610 .Nm zfs Cm create Fl V
1611 command, or by changing the reservation after the volume has been created.
1612 A
1613 .Qq sparse volume
1614 is a volume where the reservation is less than the size of the volume plus the
1615 space required to store its metadata.
1616 Consequently, writes to a sparse volume can fail with
1617 .Er ENOSPC
1618 when the pool is low on space.
1619 For a sparse volume, changes to
1620 .Sy volsize
1621 are not reflected in the reservation.  A sparse volume can be made dense
1622 .Po or
1623 .Qq not sparse
1624 .Pc
1625 by setting the reservation to
1626 .Sy auto .
1627 .It Sy vscan Ns = Ns Sy on Ns | Ns Sy off
1628 Controls whether regular files should be scanned for viruses when a file is
1629 opened and closed.
1630 In addition to enabling this property, the virus scan service must also be
1631 enabled for virus scanning to occur.
1632 The default value is
1633 .Sy off .
1634 .It Sy xattr Ns = Ns Sy on Ns | Ns Sy off
1635 Controls whether extended attributes are enabled for this file system.
1636 The default value is
1637 .Sy on .
1638 .It Sy zoned Ns = Ns Sy on Ns | Ns Sy off
1639 Controls whether the dataset is managed from a non-global zone.
1640 See the
1641 .Sx Zones
1642 section for more information.
1643 The default value is
1644 .Sy off .
1645 .El
1646 .Pp