
Table of Contents
Dec 01, 2005 mac II cx + iMac flatscreen 15, Mac OS X (10.4.3) Posted on Dec 1, 2005 1:14 PM. Not knowing linux, I can't vouch for the hdparm. Seagate Instant Secure Erase (ISE) is designed to protect data on hard disk drives by instantly resetting the drive back to factory settings and changing the encryption key so that any data remaining on the drive is cryptographically erased. This means all data on the drive is permanently and instantly unreadable. A Mac utility for setting the power management (APM) level on SATA hard drives. It can be used to eliminate 'chirping' or 'clicking when idle' noises in some HDDs. OS X 10.5 or higher. Tested up to macOS 10.12 (Sierra). Should also work with 10.13 (High Sierra). SATA hard disk with APM support. Hdparm is a good place to start. Sudo hdparm -Tt /dev/sda /dev/sda: Timing cached reads: 12540 MB in 2.00 seconds = 6277.67 MB/sec Timing buffered disk reads: 234 MB in 3.00 seconds = 77.98 MB/sec sudo hdparm -v /dev/sda will give information as well. Dd will give you information on write speed. Oct 26, 2018 Download hdparm for free. Hdparm - get/set ATA/SATA drive parameters under Linux.
Name
hdparm - get/set hard disk parameters
Synopsis
hdparm [ flags ] [device] ..
Description
hdparm provides a command line interface to various hard disk ioctlssupported by the Linux SATA/PATA/SAS “libata” subsystem and the olderIDE driver subsystem. Some options may work correctly only with thelatest kernels.

Options
When no flags are given, -acdgkmur is assumed.

- -a
- Get/set sector count for filesystem (software) read-ahead. Thisis used to improve performance in sequential reads of largefiles, by prefetching additional blocks in anticipation of thembeing needed by the running task. Many IDE drives also have aseparate built-in read-ahead function, which augments thisfilesystem (software) read-ahead function.
- -A
- Get/set the IDE drive´s read-lookahead feature (usually ON bydefault). Usage: -A0 (disable) or -A1 (enable).
- -b
- Get/set bus state.
- -B
- Set Advanced Power Management feature, if the drive supports it.A low value means aggressive power management and a high valuemeans better performance. A value of 255 will disable apm on thedrive.
- -c
- Query/enable (E)IDE 32-bit I/O support. A numeric parameter canbe used to enable/disable 32-bit I/O support: Currently supportedvalues include 0 to disable 32-bit I/O support, 1 toenable 32-bit data transfers, and 3 to enable 32-bit data transferswith a special sync sequence required by many chipsets.The value 3 works with nearly all 32-bit IDE chipsets, butincurs slightly more overhead. Note that “32-bit” refers todata transfers across a PCI or VLB bus to the interface cardonly; all (E)IDE drives still have only a 16-bit connection overthe ribbon cable from the interface card.
- -C
- Check the current IDE power mode status, which will always beone of unknown (drive does not support this command),active/idle (normal operation), standby (low power mode, drivehas spun down), or sleeping (lowest power mode, drive is completelyshut down). The -S,-y,-Y, and -Z flags can be used tomanipulate the IDE power modes.
- -d
- Disable/enable the “using_dma” flag for this drive. This optionnow works with most combinations of drives and PCI interfaceswhich support DMA and which are known to the kernel IDE driver.It is also a good idea to use the appropriate -X option in combinationwith -d1 to ensure that the drive itself is programmedfor the correct DMA mode, although most BIOSs should do this foryou at boot time. Using DMA nearly always gives the best performance,with fast I/O throughput and low CPU usage. But thereare at least a few configurations of chipsets and drives forwhich DMA does not make much of a difference, or may even slowthings down (on really messed up hardware!). Your mileage mayvary.
- --direct
- Use the kernel O_DIRECT flag when performing a -t timing test.This bypasses the page cache, causing the reads to go directlyfrom the drive into hdparm’s buffers, using so-called “raw” I/O.In many cases, this can produce results that appear much fasterthan the usual page cache method, giving a better indication ofraw device and driver performance.
- --drq-hsm-error
- VERY DANGEROUS, DON’T EVEN THINK ABOUT USING IT. This flagcauses hdparm to issue an IDENTIFY command to the kernel, butincorrectly marked as a “non-data” command. This results in thedrive being left with its DataReQust(DRQ) line “stuck” high.This confuses the kernel drivers, and may crash the system immediatelywith massive data loss. The option exists to help intesting and fortifying the kernel against similar real-worlddrive malfunctions. VERY DANGEROUS, DO NOT USE!!
- -D
- Enable/disable the on-drive defect management feature, wherebythe drive firmware tries to automatically manage defective sectorsby relocating them to “spare” sectors reserved by the factoryfor such. Control of this feature via the -D flag is notsupported for most modern drives since ATA-4; thus this commandmay fail.
- -E
- Set cdrom speed. This is NOT necessary for regular operation,as the drive will automatically switch speeds on its own. Butif you want to play with it, just supply a speed number afterthe option, usually a number like 2 or 4.
- -f
- Sync and flush the buffer cache for the device on exit. Thisoperation is also performed as part of the -t and -T timings.
- -F
- Flush the on-drive write cache buffer (older drives may notimplement this).
- -g
- Display the drive geometry (cylinders, heads, sectors), the size(in sectors) of the device, and the starting offset (in sectors)of the device from the beginning of the drive.
- -h
- Display terse usage information (help).
- -i
- Display the identification info that was obtained from the driveat boottime, if available. This is a feature of modern IDEdrives, and may not be supported by older devices. The datareturned may or may not be current, depending on activity sincebooting the system. However, the current multiple sector modecount is always shown. For a more detailed interpretation ofthe identification info, refer to ATAttachmentInterfaceforDiskDrives (ANSI ASC X3T9.2 working draft, revision 4a, April19/93).
- -I
- Request identification info directly from the drive, which isdisplayed in a new expanded format with considerably more detailthan with the older -i flag.
- --Istdin
- This is a special variation on the -I option, which accepts adrive identification block as standard input instead of using a/dev/hd* parameter. The format of this block must be exactlythe same as that found in the /proc/ide/*/hd*/identify “files',or that produced by the --Istdout option described below. Thisvariation is designed for use with collected “libraries” ofdrive identification information, and can also be used on ATAPIdrives which may give media errors with the standard mechanism.When --Istdin is used, it must be the *only* parameter given.
- --Istdout
- This option dumps the drive’s identify data in hex to stdout, ina format similar to that from /proc/ide/*/identify, and suitablefor later use with the --Istdin option.
- -k
- Get/set the keep_settings_over_reset flag for the drive. Whenthis flag is set, the driver will preserve the -dmu options overa soft reset, (as done during the error recovery sequence).This flag defaults to off, to prevent drive reset loops whichcould be caused by combinations of -dmu settings. The -k flagshould therefore only be set after one has achieved confidencein correct system operation with a chosen set of configurationsettings. In practice, all that is typically necessary to testa configuration (prior to using -k) is to verify that the drivecan be read/written, and that no error logs (kernel messages)are generated in the process (look in /var/adm/messages on mostsystems).
- -K
- Set the drive´s keep_features_over_reset flag. Setting thisenables the drive to retain the settings for -APSWXZ over a softreset (as done during the error recovery sequence). Not alldrives support this feature.
- -L
- Set the drive´s doorlock flag. Setting this to 1 will lock thedoor mechanism of some removable hard drives (eg. Syquest, ZIP,Jazz..), and setting it to 0 will unlock the door mechanism.Normally, Linux maintains the door locking mechanism automatically,depending on drive usage (locked whenever a filesystem ismounted). But on system shutdown, this can be a nuisance if theroot partition is on a removeable disk, since the root partitionis left mounted (read-only) after shutdown. So, by using thiscommand to unlock the door after the root filesystem isremounted read-only, one can then remove the cartridge from thedrive after shutdown.
- -m
- Get/set sector count for multiple sector I/O on the drive. Asetting of 0 disables this feature. Multiple sector mode (akaIDE 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 featureis enabled, it typically reduces operating system overheadfor disk I/O by 30-50%. On many systems, it also providesincreased data throughput of anywhere from 5% to 50%. Somedrives, however (most notably the WD Caviar series), seem to runslower with multiple mode enabled. Your mileage may vary. Mostdrives support the minimum settings of 2, 4, 8, or 16 (sectors).Larger settings may also be possible, depending on the drive. Asetting of 16 or 32 seems optimal on many systems. Western Digitalrecommends lower settings of 4 to 8 on many of theirdrives, due tiny (32kB) drive buffers and non-optimized bufferingalgorithms. The -i flag can be used to find the maximumsetting supported by an installed drive (look for MaxMultSect inthe output). Some drives claim to support multiple mode, butlose data at some settings. Under rare circumstances, suchfailures can result in massivefilesystemcorruption.
- -M
- Get/set Automatic Acoustic Management (AAM) setting. Most modernharddisk drives have the ability to speed down the head movementsto reduce their noise output. The possible values arebetween 0 and 254. 128 is the most quiet (and therefore slowest)setting and 254 the fastest (and loudest). Some drives have onlytwo levels (quiet / fast), while others may have different levelsbetween 128 and 254. At the moment, most drives only support3 options, off, quiet, and fast. These have been assignedthe values 0, 128, and 254 at present, respectively, but integerspace has been incorporated for future expansion, should thischange.
- -n
- Get or set the “ignore write errors” flag in the driver. Do NOTplay with this without grokking the driver source code first.
- -p
- Attempt to reprogram the IDE interface chipset for the specifiedPIO mode, or attempt to auto-tune for the “best” PIO mode supportedby the drive. This feature is supported in the kernelfor only a few “known” chipsets, and even then the support isiffy at best. Some IDE chipsets are unable to alter the PIOmode for a single drive, in which case this flag may cause thePIO mode for both drives to be set. Many IDE chipsets supporteither fewer or more than the standard six (0 to 5) PIO modes,so the exact speed setting that is actually implemented willvary by chipset/driver sophistication. Usewithextremecau_tion!This feature includes zero protection for the unwary, andan unsuccessful outcome may result in severefilesystemcorrup_tion!
- -P
- Set the maximum sector count for the drive´s internal prefetchmechanism. Not all drives support this feature, and it wasdropped from the offical spec as of ATA-4.
- -q
- Handle the next flag quietly, suppressing normal output (but noterror messages). This is useful for reducing screen clutterwhen running from system startup scripts. Not applicable to the-i or -v or -t or -T flags.
- -Q
- Set tagged queue depth (1 or greater), or turn tagged queuingoff (0). This only works with the newer 2.5.xx (or later) kernels,and only with the few drives that currently support it.
- -r
- Get/set read-only flag for the device. When set, Linux disallowswrite operations on the device.
- -R
- Register an IDE interface (DANGEROUS). See the -U option formore information.
- -s
- Enable/disable the power-on in standby feature, if supported bythe drive. VERYDANGEROUS. Do not use unless you are absolutelycertain that both the system BIOS (or firmware) and theoperating system kernel (Linux >= 2.6.22) support probing fordrives that use this feature. When enabled, the drive is powered-upin the standby mode to allow the controller to sequencethe spin-up of devices, reducing the instantaneous current drawburden when many drives share a power supply. Primarily for usein large RAID setups. This feature is usually disabled and thedrive is powered-up in the active mode (see -C above). Notethat a drive may also allow enabling this feature by a jumper.Some SATA drives support the control of this feature by pin 11of the SATA power connector. In these cases, this command may beunsupported or may have no effect.
- -S
- Set the standby (spindown) timeout for the drive. This value isused by the drive to determine how long to wait (with no diskactivity) before turning off the spindle motor to save power.Under such circumstances, the drive may take as long as 30 secondsto respond to a subsequent disk access, though most drivesare much quicker. The encoding of the timeout value is somewhatpeculiar. A value of zero means “timeouts are disabled': thedevice will not automatically enter standby mode. Values from 1to 240 specify multiples of 5 seconds, yielding timeouts from 5seconds to 20 minutes. Values from 241 to 251 specify from 1 to11 units of 30 minutes, yielding timeouts from 30 minutes to 5.5hours. A value of 252 signifies a timeout of 21 minutes. Avalue of 253 sets a vendor-defined timeout period between 8 and12 hours, and the value 254 is reserved. 255 is interpreted as21 minutes plus 15 seconds. Note that some older drives mayhave very different interpretations of these values.
- -T
- Perform timings of cache reads for benchmark and comparison purposes.For meaningful results, this operation should berepeated 2-3 times on an otherwise inactive system (no otheractive processes) with at least a couple of megabytes of freememory. This displays the speed of reading directly from theLinux buffer cache without disk access. This measurement isessentially an indication of the throughput of the processor,cache, and memory of the system under test.
- -t
- Perform timings of device reads for benchmark and comparisonpurposes. For meaningful results, this operation should berepeated 2-3 times on an otherwise inactive system (no otheractive processes) with at least a couple of megabytes of freememory. This displays the speed of reading through the buffercache to the disk without any prior caching of data. This measurementis an indication of how fast the drive can sustainsequential data reads under Linux, without any filesystem overhead.To ensure accurate measurements, the buffer cache isflushed during the processing of -t using the BLKFLSBUF ioctl.
- -u
- Get/set interrupt-unmask flag for the drive. A setting of 1permits the driver to unmask other interrupts during processingof a disk interrupt, which greatly improves Linux´s responsivenessand eliminates “serial port overrun” errors. Usethisfeaturewithcaution: some drive/controller combinations do nottolerate the increased I/O latencies possible when this featureis enabled, resulting in massivefilesystemcorruption. In particular,CMD-640B and RZ1000 (E)IDE interfaces can be unreliable(due to a hardware flaw) when this option is used with kernelversions earlier than 2.0.13. Disabling the IDEprefetch featureof these interfaces (usually a BIOS/CMOS setting) providesa safe fix for the problem for use with earlier kernels.
- -U
- Un-register an IDE interface (DANGEROUS). The companion for the-R option. Intended for use with hardware made specifically forhot-swapping (very rare!). Use with knowledge and extremecautionas this can easily hang or damage your system. The hdparmsource distribution includes a ´contrib´ directory with someuser-donated scripts for hot-swapping on the UltraBay of aThinkPad 600E. Use at your own risk.
- -v
- Display some basic settings, similar to -acdgkmur for IDE. Thisis also the default behaviour when no flags are specified.
- --verbose
- Display extra diagnostics from some commands.
- -w
- Perform a device reset (DANGEROUS). Do NOT use this option. Itexists for unlikely situations where a reboot might otherwise berequired to get a confused drive back into a useable state.
- -W
- Get/set the IDE/SATA drive´s write-caching feature.
- -x
- Tristate device for hotswap (DANGEROUS).
- -X
- Set the IDE transfer mode for newer (E)IDE/ATA drives. This istypically used in combination with -d1 when enabling DMA to/froma drive on a supported interface chipset, where -Xmdma2 is usedto select multiword DMA mode2 transfers and -Xsdma1 is used toselect simple mode 1 DMA transfers. With systems which supportUltraDMA burst timings, -Xudma2 is used to select UltraDMAmode2 transfers (you´ll need to prepare the chipset for UltraDMAbeforehand). Apart from that, use of this flag is seldomneces_sarysince most/all modern IDE drives default to their fastestPIO transfer mode at power-on. Fiddling with this can be bothneedless and risky. On drives which support alternate transfermodes, -X can be used to switch the mode of the drive only.Prior to changing the transfer mode, the IDE interface should bejumpered or programmed (see -p flag) for the new mode setting toprevent loss and/or corruption of data. Usethiswithextremecaution! For the PIO (Programmed Input/Output) transfer modesused by Linux, this value is simply the desired PIO mode numberplus 8. Thus, a value of 09 sets PIO mode1, 10 enables PIOmode2, and 11 selects PIO mode3. Setting 00 restores thedrive´s “default” PIO mode, and 01 disables IORDY. For multiwordDMA, the value used is the desired DMA mode number plus 32.for UltraDMA, the value is the desired UltraDMA mode number plus64.
- -y
- Force an IDE drive to immediately enter the low power consumptionstandby mode, usually causing it to spin down. The currentpower mode status can be checked using the -C flag.
- -Y
- Force an IDE drive to immediately enter the lowest power consumptionsleep mode, causing it to shut down completely. A hardor soft reset is required before the drive can be accessed again(the Linux IDE driver will automatically handle issuing a resetif/when needed). The current power mode status can be checkedusing the -C flag.
- -z
- Force a kernel re-read of the partition table of the specifieddevice(s).
- -Z
- Disable the automatic power-saving function of certain Seagatedrives (ST3xxx models?), to prevent them from idling/spinningdownat inconvenient times.
- -H
- Read the temperature from some (mostly Hitachi) drives. Alsoreports if the temperature is within operating condition range(this may not be reliable). Does not cause the drive to spin upif idle.
ATASecurityFeatureSet
These switches are DANGEROUS to experiment with, and might not workwith every kernel. USEATYOUROWNRISK.
- --security-help
- Display terse usage info for all of the --security-* flags.
- --security-freeze
- Freeze the drive´s security settings. The drive does not acceptany security commands until next power-on reset. Use this functionin combination with --security-unlock to protect drive fromany attempt to set a new password. Can be used standalone, too.
- --security-unlockPWD
- Unlock the drive, using password PWD. Password is given as anASCII string and is padded with NULs to reach 32 bytes. Theapplicable drive password is selected with the --user-masterswitch. THISFEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
- --security-set-passPWD
- Lock the drive, using password PWD (Set Password) (DANGEROUS).Password is given as an ASCII string and is padded with NULs toreach 32 bytes. The applicable drive password is selected withthe --user-master switch and the applicable security mode withthe --security-mode switch. THISFEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
- --security-disablePWD
- Disable drive locking, using password PWD. Password is given asan ASCII string and is padded with NULs to reach 32 bytes. Theapplicable drive password is selected with the --user-masterswitch. THISFEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
- --security-erasePWD
- Erase (locked) drive, using password PWD (DANGEROUS). Passwordis given as an ASCII string and is padded with NULs to reach 32bytes. The applicable drive password is selected with the--user-master switch. THISFEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
- --security-erase-enhancedPWD
- Enhanced erase (locked) drive, using password PWD (DANGEROUS).Password is given as an ASCII string and is padded with NULs toreach 32 bytes. The applicable drive password is selected withthe --user-master switch. THISFEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
- --user-masterUSER
- Specifies which password (user/master) to select. Defaultstomaster. Only useful in combination with --security-unlock,--security-set-pass, --security-disable, --security-erase or--security-erase-enhanced.
- u
- user password
- m
- master password
- THIS
- FEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
- --security-modeMODE
- Specifies which security mode (high/maximum) to set. Defaultstohigh. Only useful in combination with --security-set-pass.
- h
- high security
- m
- maximum security
- THIS
- FEATUREISEXPERIMENTALANDNOTWELLTESTED.USEATYOUROWNRISK.
Bugs
As noted above, the -msectcount and -u1 options should be used withcaution at first, preferably on a read-only filesystem. Most driveswork well with these features, but a few drive/controller combinationsare not 100% compatible. Filesystem corruption may result. Backupeverything before experimenting!

Some options (eg. -r for SCSI) may not work with old kernels as necessaryioctl()´s were not supported.
Although this utility is intended primarily for use with (E)IDE harddisk devices, several of the options are also valid (and permitted) foruse with SCSI hard disk devices and MFM/RLL hard disks with XT interfaces.
The Linux kernel up until 2.6.12 (and probably later) doesn´t handlethe security unlock and disable commands gracefully and will segfaultand in some cases even panic. The security commands however mightindeed have been executed by the drive. This poor kernel behaviourmakes the PIO data security commands rather useless at the moment.
Note that the “security erase” and “security disable” commands havebeen implemented as two consecutive PIO data commands and will not succeedon a locked drive because the second command will not be issuedafter the segfault. See the code for hints how patch it to work aroundthis problem. Despite the segfault it is often still possible to runtwo instances of hdparm consecutively and issue the two necessary commandsthat way.
Author
hdparm has been written by Mark Lord <mlord@pobox.com>, the originalprimary developer and maintainer of the (E)IDE driver for Linux, withsuggestions from many netfolk.
The disable Seagate auto-powersaving code is courtesy of Tomi Leppikangas(tomilepp@paju.oulu.fi).
Hdparm For Macbook
Security freeze command by Benjamin Benz <bbe@heise.de>, 2005.
PIO data out security commands by Leonard den Ottolander <leonard denottolander nl>, 2005. Parts by Benjamin Benz <bbe@heise.de> and others.
SeeAlso
http://www.t13.org/ Technical Committee T13 AT Attachment (ATA/ATAPI)Interface.
http://www.serialata.org/ Serial ATA International Organization.
http://www.compactflash.org/ CompactFlash Association
Erasing your disk: For most reasons to erase, including when reformatting a disk or selling, giving away, or trading in your Mac, you should erase your entire disk.
Erasing a volume on your disk: In other cases, such as when your disk contains multiple volumes (or partitions) and you don't want to erase them all, you can erase specific volumes on the disk.
Erasing a disk or volume permanently deletes all of its files. Before continuing, make sure that you have a backup of any files that you want to keep.
How to erase your disk
- Start up from macOS Recovery. Then select Disk Utility from the Utilities window and click Continue.
If you're not erasing the disk your Mac started up from, you don't need to start up from macOS Recovery: just open Disk Utility from the Utilities folder of your Applications folder.
- Choose View > Show All Devices from the menu bar in Disk Utility. The sidebar now shows your disks (devices) and any containers and volumes within them. The disk your Mac started up from is at the top of the list. In this example, Apple SSD is the startup disk:
- Select the disk that you want to erase. Don't see your disk?
- Click Erase, then complete these items:
- Name: Type the name that you want the disk to have after you erase it.
- Format: Choose APFS or Mac OS Extended (Journaled). Disk Utility shows a compatible format by default.
- Scheme: Choose GUID Partition Map.
- Click Erase to begin erasing your disk and every container and volume within it. You might be asked to enter your Apple ID. Forgot your Apple ID?
- When done, quit Disk Utility.
- If you want your Mac to be able to start up from the disk you erased, reinstall macOS on the disk.
How to erase a volume on your disk
- Start up from macOS Recovery. Then select Disk Utility from the Utilities window and click Continue.
If you're not erasing the volume your Mac started up from, you don't need to start up from macOS Recovery: just open Disk Utility from the Utilities folder of your Applications folder. - In the sidebar of Disk Utility, select the volume that you want to erase. The volume your Mac started up from is named Macintosh HD, unless you changed its name. Don't see your volume?
- Click Erase, then complete these items:
- Name: Type the name that you want the volume to have after you erase it.
- Format: Choose APFS or Mac OS Extended (Journaled). Disk Utility shows a compatible format by default.
- If you see an Erase Volume Group button, the volume you selected is part of a volume group. In that case, you should erase the volume group. Otherwise, click Erase to erase just the selected volume. You might be asked to enter your Apple ID. Forgot your Apple ID?
- When done, quit Disk Utility.
- If you want your Mac to be able to start up from the volume you erased, reinstall macOS on that volume.
Reasons to erase
You can erase at any time, including in circumstances such as these:
- You want to permanently erase all content from your Mac and restore it to factory settings. This is one of the final steps before selling, giving away, or trading in your Mac.
- You're changing the format of a disk, such as from a PC format (FAT, ExFAT, or NTFS) to a Mac format (APFS or Mac OS Extended).
- You received a message that your disk isn't readable by this computer.
- You're trying to resolve a disk issue that Disk Utility can't repair.
- The macOS installer doesn't see your disk or can't install on it. For example, the installer might say that your disk isn't formatted correctly, isn't using a GUID partition scheme, contains a newer version of the operating system, or can't be used to start up your computer.
- The macOS installer says that you may not install to this volume because it is part of an Apple RAID.
About APFS and Mac OS Extended
Hdparm For Mac Pro
Disk Utility in macOS High Sierra or later can erase using either the newer APFS (Apple File System) format or the older Mac OS Extended format, and it automatically chooses a compatible format for you.
How to choose between APFS and Mac OS Extended
Hdparm For Mac Catalina
Disk Utility tries to detect the type of storage and show the appropriate format in the Format menu. If it can't, it chooses Mac OS Extended, which works with all versions of macOS. If you want to change the format, answer these questions:
- Are you formatting the disk that came built into your Mac?
If the built-in disk came APFS-formatted, Disk Utility suggests APFS. Don't change it to Mac OS Extended. - Are you about to install macOS High Sierra or later for the first time on the disk?
If you need to erase your disk before installing High Sierra or later for the first time on that disk, choose Mac OS Extended (Journaled). During installation, the macOS installer decides whether to automatically convert to APFS—without erasing your files. - Are you preparing a Time Machine backup disk or bootable installer?
Choose Mac OS Extended (Journaled) for any disk that you plan to use as a Time Machine backup disk or as a bootable installer. - Will you be using the disk with another Mac?
If the other Mac isn't using macOS High Sierra or later, choose Mac OS Extended (Journaled). Earlier versions of macOS don't work with APFS-formatted volumes.
How to identify the format currently in use
If you want to know which format is currently in use, use any of these methods:
- Select the volume in the Disk Utility sidebar, then check the information shown on the right. For more detail, choose File > Get Info from the Disk Utility menu bar.
- Open System Information and select Storage in the sidebar. The File System column on the right shows the format of each volume.
- Select the volume in the Finder, then choose File > Get Info from the menu bar. The Get Info window shows the Format of that volume.
If your disk or volume doesn't appear, or the erase fails
- Shut down your Mac, then unplug all nonessential devices from your Mac.
- If you're erasing an external drive, make sure that it's connected directly to your Mac using a cable that you know is good. Then turn the drive off and back on.
- If your disk or volume still doesn't appear in Disk Utility, or Disk Utility reports that the erase process failed, your disk or Mac might need service. If you need help, please contact Apple Support.
Learn more
Hdparm Mac Alternative
- If you can't start up from macOS Recovery, you can use a different startup disk instead.
- If Disk Utility shows a Security Options button in the Erase window, you can click that button to choose between a faster (but less secure) erase and a slower (but more secure) erase. Some older versions of Disk Utility offer the option to zero all data instead. These secure-erase options aren't offered or needed for solid-state drives (SSDs) and flash storage.