# I wish to verify the maximum usable capacity of a disk drive



## byrnejb (Mar 3, 2020)

I wish to determine if the system I am using will actually support HDDs of 8Tb or more.  What is the easiest way to do that assuming that I am starting with a single disk and an installer usb with FreeBSD-12.1.


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## ralphbsz (Mar 3, 2020)

It will support them, guaranteed. Lots of people use much bigger disk drives; individual disk drives ship with capacities up to 16 or 18 TB, and FreeBSD can use disk drives that are implemented by external RAID controllers and can be much larger. The only possible exception to that would be if you are using a very very obsolete HBA (disk adapter), but that's highly unlikely.

Assuming that you are connecting your disk directly to the motherboard: even the motherboard does not play a role in this, since FreeBSD doesn't use BIOS functions to read/write the disk drive, and problems of not being able to boot from oversize disk drives have not existed for about 20 years.

If you don't believe it: Start the installer in rescue or live mode, and run either of commands "camcontrol readcap" (for SCSI disks, which I think includes most USB-connected disks), or "camcontrol identify" (for ATA disks), and it will give you the capacity.


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## byrnejb (Mar 3, 2020)

I am trying to pin down a problem that caused a boot-on-zfs host to fail to boot.  I have replaced the boot code on each of the four drives in the pool, which is a raidz2, and rebooted without success.  My suspicion was that perhaps the disk controller "wrapped around" a write at some point and clobbered the meta data.  If this is indeed an impossibility then I will look at the next suspect.

Below is what the disk utilities show which matches exactly what is expected, a nominal 8Tb drive.



```
diskinfo -v ada0
ada0
    512             # sectorsize
    8001563222016    # mediasize in bytes (7.3T)
    15628053168     # mediasize in sectors
    4096            # stripesize
    0               # stripeoffset
    15504021        # Cylinders according to firmware.
    16              # Heads according to firmware.
    63              # Sectors according to firmware.
    WDC WD80EFAX-68KNBN0    # Disk descr.
    VAH3PXYL        # Disk ident.
    No              # TRIM/UNMAP support
    5400            # Rotation rate in RPM
    Not_Zoned       # Zone Mode



camcontrol identify ada0
pass1: <WDC WD80EFAX-68KNBN0 81.00A81> ACS-2 ATA SATA 3.x device
pass1: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)

protocol              ACS-2 ATA SATA 3.x
device model          WDC WD80EFAX-68KNBN0
firmware revision     81.00A81
serial number         VAH3PXYL
WWN                   5000cca099cfc6f4
additional product id
cylinders             16383
heads                 16
sectors/track         63
sector size           logical 512, physical 4096, offset 0
LBA supported         268435455 sectors
LBA48 supported       15628053168 sectors
PIO supported         PIO4
DMA supported         WDMA2 UDMA6
media RPM             5400
Zoned-Device Commands no

Feature                      Support  Enabled   Value           Vendor
read ahead                     yes    yes
write cache                    yes    yes
flush cache                    yes    yes
Native Command Queuing (NCQ)   yes        32 tags
NCQ Priority Information       yes
NCQ Non-Data Command           yes
NCQ Streaming                  yes
Receive & Send FPDMA Queued    yes
NCQ Autosense                  yes
SMART                          yes    yes
security                       yes    no
power management               yes    yes
microcode download             yes    yes
advanced power management      yes    yes    164/0xA4
automatic acoustic management  no    no
media status notification      no    no
power-up in Standby            yes    no
write-read-verify              no    no
unload                         no    no
general purpose logging        yes    yes
free-fall                      no    no
sense data reporting           yes    no
extended power conditions      yes    no
device statistics notification no    no
Data Set Management (DSM/TRIM) no
Trusted Computing              no
encrypts all user data         no
Sanitize                       yes        overwrite,
Sanitize - commands allowed    yes
Sanitize - antifreeze lock     no
Host Protected Area (HPA)      yes      no      15628053168/15628053167
HPA - Security                 yes      no
Accessible Max Address Config  no
```


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## ralphbsz (Mar 3, 2020)

I don't think "wrap around" is the problem here. The problem must be something else. Could it be the partitioning? Check that your partition tables make sense. When you say "boot-on-zfs host to fail to boot", what are the exact symptoms? If we have error messages, we might be able to guess the root cause.


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## byrnejb (Mar 5, 2020)

The underlying issue proved to be a problem with the motherboard.   When the disks were pulled and put into another chassis they booted that system.  There is a separate thread dealing with this, on which you have commented.


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