svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.
ada(4)
The driver provides support for direct access devices, implement‐
ing the command protocol, that are attached to the system through
a host adapter supported by the CAM subsystem. The host adapter
must also be separately configured into the system before an di‐
rect access device can be configured. Command queuing allows the
device to process multiple transactions concurrently, often re-
ordering them to reduce the number and length of seeks. defines
two types of queuing: and The device driver takes full advantage
of NCQ, when supported. To ensure that transactions to distant
parts of the media, which may be deferred indefinitely by servic‐
ing requests closer to the current head position, are completed
in a timely fashion, an ordered transaction is sent every 7 sec‐
onds during continuous device operation. Many direct access de‐
vices are equipped with read and/or write caches. Parameters af‐
fecting the device's cache are reported in device IDENTIFY data
and can be examined and modified via the utility. The read cache
is used to store data from device-initiated read ahead operations
as well as frequently used data. The read cache is transparent
to the user and can be enabled without any adverse effect. Most
devices with a read cache come from the factory with it enabled.
The write cache can greatly decrease the latency of write opera‐
tions and allows the device to reorganize writes to increase ef‐
ficiency and performance. This performance gain comes at a
price. Should the device lose power while its cache contains un‐
committed write operations, these writes will be lost. The ef‐
fect of a loss of write transactions on a file system is non-de‐
terministic and can cause corruption. Most devices age write
transactions to limit the vulnerability to a few transactions re‐
cently reported as complete, but it is nonetheless recommended
that systems with write cache enabled devices reside on an Unin‐
terruptible Power Supply (UPS). The device driver ensures that
the cache and media are synchronized upon final close of the de‐
vice or an unexpected shutdown (panic) event. This ensures that
it is safe to disconnect power once the operating system has re‐
ported that it has halted. The following variables are available
as both variables and tunables: This variable determines how many
times the driver will retry a READ or WRITE command. This does
not affect the number of retries used during probe time or for
the driver dump routine. This value currently defaults to 4.
This variable determines how long the driver will wait before
timing out an outstanding command. The units for this value are
seconds, and the default is currently 30 seconds. This variable
determines whether to spin-down disks when shutting down. Set to
1 to enable spin-down, 0 to disable. The default is currently
enabled. These variables determine whether request queue should
be sorted trying to optimize head seeks. Set to 1 to enable
sorting, 0 to disable, -1 to leave it as-is. The default is
sorting enabled for HDDs and disabled SSDs. These variables de‐
termine whether device read-ahead and write caches should be en‐
abled globally or per-device or disabled. Set to 1 to enable
write cache, 0 to disable, -1 to leave it as-is. Values modified
at runtime take effect only after device reset Because of that,
this setting should be changed in instead of The global default
is currently 1. The per-device default is to leave it as-is
(follow global setting). ATA device nodes The driver first ap‐
peared in