On 2014-08-03 15:57 (GMT-0400) Felix Miata composed:
> On 2014-08-03 13:16 (GMT) hcvv composed:
>> …but once it comes to the level of device files (disks and partitions as
>> found in /dev) there is no difference anymore (after all, one of the
>> main task of an operating system is to hide hardware from higher level
>> programming and the user).
>> when the disk is always connected the difference between “internal” and
>> “external” is of no influence.
> Possibly true if the issue is USB3 vs. eSATA, but for USB1 or USB2 vs. eSATA,
> throughput makes a bit difference to anyone using it for boot or working with
> large files. eSATA is typically somewhere in the vicinity of at least 2.5X as
> fast as USB2. Actual example:
> 7200 RPM 2TB Seagate:
> Model=ST2000DM001-1CH164, FwRev=CC27, SerialNo=W1E54Y73
> UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
> Drive conforms to: Reserved: ATA/ATAPI-4,5,6,7
> Installed in:
> # hdparm -t:
> connected as /dev/sdb via eSATA on NM10/ICH7 SATA interface:
> Timing buffered disk reads: 536 MB in 3.01 seconds = 178.34 MB/sec
> connected as /dev/sdb via USB2 on NM10/ICH7 EHCI interface:
> Timing buffered disk reads: 106 MB in 3.03 seconds = 34.95 MB/sec
> For this example, eSATA is reading the same device without benefit of cache
> at 5.1X the speed of USB2.
> IOW, for booting from external HD, you should prefer a connection faster than
> USB2 if performance on a level similar to an internal HD is wanted.
A different HD, 5400 RPM laptop drive, connected through:
Model=WDC WD5000LPVX-00V0TT0, FwRev=01.01A01, SerialNo=WD-WX11A54M6007
UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7
connected as /dev/sdb via eSATA on ICH7R interface:
Timing buffered disk reads: 286 MB in 3.01 seconds = 94.88 MB/sec
connected as /dev/sdb via USB2 interface:
Timing buffered disk reads: 96 MB in 3.02 seconds = 31.75 MB/sec
For this example, eSATA is reading the same device without benefit of cache
at 2.99X the speed of USB2.
The wise are known for their understanding, and pleasant
words are persuasive.
Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!
Felix Miata *** http://fm.no-ip.com/