[Gllug] Current advice for HD purchase ...

[John Edwards]

On Wed, Mar 04, 2009 at 03:18:16PM +0000, Karanbir Singh wrote:
> Peter Corlett wrote:
>> The USB 2 wire speed is 60MB/s, but protocol overhead means that the  
>> useful maximum throughput is about 30MB/s in practice.
> 
> most specs I seem to come across seem to say 480Mbps, but I am guessing 
> that is just specified capability. Reaching those speeds might be harder.

Just in case there is any confusion:
480Mbps (Mega bits per second) = 60MBps (Mega bytes per second)


> But that 30MB/sec number looks quite low, will try and find a usb device 
> that I could test with.

Maxtor STM310003 1TB SATA2 drive in a USB2 enclosure:
--------
$ /sbin/hdparm -Tt /dev/sde

/dev/sde:
 Timing cached reads:   7680 MB in  2.00 seconds = 3846.36 MB/sec
 Timing buffered disk reads:   98 MB in  3.05 seconds =  32.17 MB/sec
--------



>> The 160GB Seagate disks I bought in 2005 can read off the platter at  
>> 60MB/s. When replaced with 500GB disks in 2008, the performance went  
>> up to 100MB/s.
> 
> I've not seen a single spindle get upto those speeds, even when attached 
> to sas/sata/scsi interfaces. What did are you checking where you get 
> these speeds ? Although you do say 'disks' implying there might be more 
> than 1 spindle involved.....

Similar Maxtor STM310003 1TB SATA2 drive connected via SATA2:
--------
/sbin/hdparm -Tt /dev/sdb

/dev/sdb:
 Timing cached reads:   7440 MB in  2.00 seconds = 3722.95 MB/sec
 Timing buffered disk reads:  284 MB in  3.02 seconds =  94.11 MB/sec
--------

That's about 3 times as fast, and those Maxtor drives were just
standard desktop drives (under 100UKP last year).


-- 
#---------------------------------------------------------#
|    John Edwards   Email: john at cornerstonelinux.co.uk    |
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