On Friday 16 December 2005 12:25, Joshua Baker-LePain wrote:
>On Fri, 16 Dec 2005 at 12:08pm, Gene Heskett wrote
>
>> On Friday 16 December 2005 11:42, Joshua Baker-LePain wrote:
>>> A single drive is going to have an awfully hard time... scratch
>>> that. A single drive can *not* feed an lto3 drive as fast as it
>>> wants to be fed (even if that's the only thing it's trying to do).
>>>  I've got a 4 disk hardware RAID0 feeding my lto3 drive.
>>
>> Ahh, I'd argue that point Roy.  Of the two active drives on this
>> machine, the main one is a 120GB, and I'm using a 200G as virtual
>> disk.  These are on seperate cables of the same on board nforce2
>> controller.  As all drives here have dma enabled, the hdparm -tT
>> test returns are typically in the 50-60 mb/second rate.  I did have
>> a scsi controller in here at one time but the tape died so it was
>> removed. But while it was installed, I was able to get 20mg/second
>> transfers to another smallish scsi drive hooked up temporarily. 
>> The drive was rated as scsi-2-fast, as was the advansys controller.
>
>Overland's datasheet for my Neo2K says the native transfer rate w/ 1
> LTO3 drive is 288GB/hour, which translates to 80MB/s.  LTO3 drives
> are *fast*. AIUI, they'll throttle down to 1/2 that without starting
> DLT-like shoe-shining behavior, but even 40MB/s is pretty quick.
>
>> If this user is only getting 2.5mb/sec, something is wrong with the
>> config someplace.  I'd start with the hdparm -Tt /dev/whatever
>> tests and see if the dma can be enabled all across the board.
>
>Oh, absolutely.  He should definitely be getting better speeds than
> he is. I was simply pointing out that a single disk holding area
> ain't gonna' cut it in production for lto3.

That almost sounds like he would need a dedicated hardware raid to use 
as a holdng disk then.  Ouch. And maybe futile unless that same 
controller can also handle the tape & library, in which case the 
devices could negotiate their own transfers between themselves, at 
whatever the limiting speed of the cable might be.  This library is I 
take it, a scsi3 wide interface? 320mb/sec rated?

-- 
Cheers, Gene
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