Hdparm: differenze tra le versioni

; -a : Get/set sector count for filesystem read-ahead. This is used to improve performance in sequential reads of large files, by  prefetching  additional blocks  in  anticipation  of  them being needed by the running task.  In the current kernel version (2.0.10) this has a default setting of 8 sectors (4KB).  This value seems good for most purposes, but in a system where most file accesses are random seeks, a smaller setting might  provide  better performance.  Also, many IDE drives also have a separate built-in read-ahead function, which alleviates the need for a filesystem read-ahead in many situations.

; -A : Disable/enable the IDE drive's read-lookahead feature (usually ON by default).  Usage: -A0 (disable) or -A1 (enable).

; -B : Set Advanced Power Management feature, if the drive supports it. A low value means aggressive power management and a high value means better performance. A value of 255 will disable apm on the drive.

; -c : Query/enable  (E)IDE 32-bit I/O support.  A numeric parameter can be used to enable/disable 32-bit I/O support: Currently supported values include 0 to disable 32-bit I/O support, 1 to enable 32-bit data transfers, and 3 to enable 32-bit data transfers with a special  sync  sequence  required  by many  chipsets.  The value 3 works with nearly all 32-bit IDE chipsets, but incurs slightly more overhead.  Note that "32-bit" refers to data transfers across a PCI or VLB bus to the interface card only; all (E)IDE drives still have only a 16-bit connection over the ribbon cable from the interface card.

; -m : Get/set  sector  count for multiple sector I/O on the drive.  A setting of 0 disables this feature.  Multiple sector mode (aka IDE Block Mode), is a feature of most modern IDE hard drives, permitting the transfer of multiple sectors per I/O interrupt, rather than the usual one sector  per  interrupt.  When  this  feature  is  enabled,  it typically reduces operating system overhead for disk I/O by 30-50%.  On many systems, it also provides increased data throughput of anywhere from 5% to 50%.  Some drives, however (most notably the WD Caviar series), seem to run  slower  with  multiple mode  enabled.  Your mileage may vary.  Most drives support the minimum settings of 2, 4, 8, or 16 (sectors).  Larger settings may also be possible,  depending on the drive.  A setting of 16 or 32 seems optimal on many systems.  Western Digital recommends lower settings of 4 to 8 on many of  their drives,  due  tiny (32kB) drive buffers and non-optimized buffering algorithms.  The -i flag can be used to find the maximum setting supported by an installed drive (look for MaxMultSect in the output).  Some drives claim to support multiple mode, but lose data at some settings.  Under rare  circumstances, such failures can result in massive filesystem corruption.

; -M : Get/set  Automatic  Acoustic Management (AAM) setting. Most modern harddisk drives have the ability to speed down the head movements to reduce their  noise output.  The possible values are between 0 and 254. 128 is the most quiet (and therefore slowest) setting and 254 the fastest  (and  loudest). Some  drives  have only two levels (quiet / fast), while others may have different levels between 128 and 254.  THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.

; -p : Attempt to reprogram the IDE interface chipset for the specified PIO mode, or attempt to auto-tune for the "best" PIO mode supported by  the  drive. This feature is supported in the kernel for only a few "known" chipsets, and even then the support is iffy at best.  Some IDE chipsets are unable to alter the PIO mode for a single drive, in which case this flag may cause the PIO mode for both drives to be set.  Many IDE chipsets  support  either fewer  or more than the standard six (0 to 5) PIO modes, so the exact speed setting that is actually implemented will vary by chipset/driver sophis tication.  Use with extreme caution!  This feature includes zero protection for the unwary,  and  an  unsuccessful  outcome  may  result  in  severe filesystem corruption!

; -P : Set the maximum sector count for the drive's internal prefetch mechanism.  Not all drives support this feature.

; -w : Perform a device reset (DANGEROUS).  Do NOT use this option.  It exists for unlikely situations where a reboot might otherwise be required to get  a confused drive back into a useable state.

; -W : Disable/enable the IDE drive's write-caching feature (default state is undeterminable; manufacturer/model specific).

; -X :    Set  the  IDE transfer mode for newer (E)IDE/ATA drives.  This is typically used in combination with -d1 when enabling DMA to/from a drive on a sup ported interface chipset, where -X mdma2 is used to select multiword DMA mode2 transfers and -X sdma1 is used to select simple mode 1 DMA transfers. With  systems  which  support  UltraDMA  burst  timings, -X udma2 is used to select UltraDMA mode2 transfers (you'll need to prepare the chipset for UltraDMA beforehand).  Apart from that, use of this flag is seldom necessary since most/all modern IDE drives default to their fastest PIO  transfer mode  at  power-on.  Fiddling with this can be both needless and risky.  On drives which support alternate transfer modes, -X can be used to switch the mode of the drive only.  Prior to changing the transfer mode, the IDE interface should be jumpered or programmed (see -p flag) for the new  mode setting  to  prevent  loss  and/or corruption of data.  Use this with extreme caution!  For the PIO (Programmed Input/Output) transfer modes used by Linux, this value is simply the desired PIO mode number plus 8.  Thus, a value of 09 sets PIO mode1, 10 enables PIO mode2, and 11 selects PIO mode3. Setting  00  restores  the drive's "default" PIO mode, and 01 disables IORDY.  For multiword DMA, the value used is the desired DMA mode number plus 32.  for UltraDMA, the value is the desired UltraDMA mode number plus 64.

:* PIO mode

:** '''4''' -X68 66MB/sec UDMA66

:** '''5''' -x69 100MB/sec UDMA100  

; -Y : Force  an  IDE  drive  to  immediately  enter  the lowest power consumption sleep mode, causing it to shut down completely.  A hard or soft reset is required before the drive can be accessed again (the Linux IDE driver will automatically handle issuing a reset if/when needed).  The current  power mode status can be checked using the -C flag.

=Test delle Performance=