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RE: [PLUG] SCSI RAID Drive array (Internal vs External)
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> -----Original Message-----
> From: plug-bounces@lists.phillylinux.org
> [mailto:plug-bounces@lists.phillylinux.org] On Behalf Of Steve Morgan
> Sent: Friday, August 04, 2006 10:26 AM
> To: Philadelphia Linux User's Group Discussion List
> Subject: Re: [PLUG] SCSI RAID Drive array (Internal vs External)
>
> I do not believe you need to worry about the speed of the
> data transfer between internal versus external devices. In
> my opinion, the transfer of data between the host card and
> the harddrives should be the same whether they are internally
> or externally connected. The host card is rated for a
> certain speed and it delivers it to all connections.
>
> It would depend on the type of external box you buy for the
> disks. Do also take into consideration whether your host
> card's external interface is Differential or Single-ended
> SCSI. I have two types of external enclosures in my
> apartment. One type of box just holds a bunch of disks and
> conencts them all and dumps them onto the SCSI chain. These
> harddrives are seen to the host controller as Just a Bunch of
> Disks (JBOD). The operating system will see each individual
> harddrive and will work with it as it pleases. This external
> box connects to the host via Single-ended. The other type of
> box I have connects to the host via Differential SCSI and
> does all of the RAID interally, meaning you configure all the
> drives in whatever configuration(s) you wish on the device
> itself and the host computer will see those as such. A
> simple configuration I have setup is all 12 drvies are set up
> using RAID 0 striping. This presents to the host computer as
> a single large drive. All of the RAID logic is being done on
> the external box itself with dedicated hardware, whereas with
> a JBOD setup all the RAID logic would be software based with
> the operating system.
>
> Depending on how you operate your RAID, whether it is
> software based with the operating system or hardware based
> with a dedicated external box or a SCSI controller with RAID
> capabilities, it will dictate what kind of setup you will end
> up with. I amdit I am not the best SCSI expert on this list,
> but if I need to clarify anything for you please feel free to
> respond on or off list. I invite others to offer their
> opinions and to correct me on my information should it be wrong.
>
>
> Steve Morgan
>
>
>
>
> On 8/4/06, George Gallen <ggallen@slackinc.com> wrote:
>
> Since we are planning for a new system, I'm considering
> making our
> data drives (which are currently internal SCSI RAID
> card - 0+1) an external
> drive bay, so if we had to switch to a another system
> down the road, moving
> the data would be as simple as disconnect and reconnect.
>
> Is there any drawback to hooking up the drives to the
> external port of a
> SCSI controller, vs the internal port? Speed differences?
>
> We currently have a 10 drive RAID 0+1, 5 (18gb) drives
> striped and mirrored.
> This is for a database server, it was suggested by IBM
> that we stripe out the
> drives to make for faster reads.
>
> If we go external, does the server still handle the
> RAIDing, or does the drive
> bay enclosure handle the RAIDing, and it just appears
> as one SCSI device to
> the server?
>
> George
>
> George Gallen
> Senior Programmer/Analyst
> Accounting/Data Division
> ggallen@slackinc.com
> ph:856.848.1000 Ext 220
>
> SLACK Incorporated - Delivering the best in health care
> information and education worldwide.
> http://www.slackinc.com
>
>
>
>
> ______________________________________________________________
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>
>
>
Cable quality and length will affect performance.
-C
"Give a man a fish and you feed him for a day; give him a freshly-charged
Electric Eel and chances are he won't bother you for anything ever again."
-- Tanuki
___________________________________________________________________________
Philadelphia Linux Users Group -- http://www.phillylinux.org
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