[olug] SAN Information

Fri Sep 27 19:09:36 UTC 2002

The software depends on how fancy you want to be.  If you use LUN masking
etc. in the controller or switch then each host can only see the LUN the
controller lets it see via hardware addressing on the loop.  Now some say
that is not a true SAN but I use the definition that multiple hosts are
using one physical disk array so I call it a SAN.  Now if you add software
to the mix then a whole bucket of possibilities opens up.  You can choose
Veritas or the software from the SAN vendor.  In this case the SAN is more
like another host on the loop but it's job is to store and retrieve data
to/from the disks.  These more advanced SANs allow you to do all sorts of
cool things like have been discussed (volume management, filesystem
resizing, cache stripe optimization, disk block size masking and the like).
In that environment the host never really "owns" the data is how I look at
it.  The data belongs to the SAN and it is served to the host as it requests
it.

In my environment the host really owns the data because it probes the loop
for the LUNs and then attaches to them and will get really mad if it does
not see them (it is not a virtual volume).  What is cool is that if you use
fibre channel drives and fibre controllers they are all dual attached by
design.  So you can build a completely separate data path to the disks for
redundancy if you want to.  Again the more you add the more you pay.  In
Sun's case they have redundant interface software that watches for hardware
failure and can switch to the secondary path if needed.  This is basically
Veritas software under the covers.  The really big arrays spend a lot of
effort to make them fast.  Some big Hitachi units have over 10GB of disk
cache (ram) that the CPU manages to allocate the writes in the most
efficient manner.  There is a world of difference between what I use and
those units.  We wanted something reasonable in cost, expandable, reliable
and vendor neutral for upgrading in the future.  So we built our system.

John

-----Original Message-----
From: roger schmeits [mailto:schmeits at clarksoncollege.edu]
Sent: Friday, September 27, 2002 1:25 PM
To: olug at olug.org
Subject: Re: [olug] SAN Information

Ok. lets say we build the SANs. Buy all the hardware ans so forth. Dont
you need software to interface with the different o/s?

That where it gets pricey right?  I understand the hardware part but I
thought there had to something in between the servers.

Please correct me if I am wrong.

Congrads on building your own SANs ..impressive..

On Fri, 2002-09-27 at 11:09, Rogers, John C NWD02 wrote:
> HI all, 
> I know I have not made it to any meetings and only reply when I think I
> have relevant information so here are some ideas on the SAN.
> 
> At my office I designed and built a Fibre SAN that we use on our Solaris
> boxes.  It was built from scratch so we know every part in it and who
> made it.  In my research there are many vendors but they all would not
> share the basic information with us about who made the controller, what
> FC card are they using, what disk drives, can I get any drive and use
> them...  They like to sell the "System" so you are married to them from
> that point on.
> 
> Well I did not like the fact that if I purchased a 15 bay disk rack with
> say 5 drives populated I had to purchase the drives and canisters from
> the vendor to expand in the future.  So I kept searching because all the
> vendors were charging way over market value for standard off the shelf
> disk drives (just for the hunk of sheet metal that holds the disk). I
> found a very good vendor that produces the actual metal drive enclosure
> and drive canisters.  They will also sell you any controller from a list
> they represent: (CMD Titan Series, Viper Series; Digi-Data Fibre Sabre,
> 9500 Series, 9200 Series, 9100 Series, Fascore; Infortrend EON Series,
> Sentinel Series, IFT-3102 Series, IFT-3101 Series; Chaparral K7413 Fibre
> to SCSI, K5412 Ultra2 to Ultra2.
> 
>   
> I have to say that the metal work and board work on these cabinets is
> first rate, they use three 300 watt power supplies, can do full SAFETY
> monitoring of temperature and other environmental conditions.  We have
> purchased three boxes made by these guys two 18 bay and one 9 bay.  Both
> have been very well made.  Supposedly they built the RAIDs for Yahoo (a
> 9 bay Jaguar with DigiData controllers).  
> 
> Anyway we have about 1.4TB online on our two big racks and 144GB on the
> small rack.  We have a mix of drives from 36GB to the 181GB disks making
> up the tiers/LUNS and have no problems.  We chose the DigiData
> controller SCSI to the disk, Fibre to the host, Emulex LP8000 on the
> host adapter.  You can make them as complicated as you want.  LUN mask,
> mask by WWN or use a smart FC hub or switch (Gadzooks or Emulex).  I
> think we have about $20K in our system so far but can replace disks at
> any time with any size etc for a long life expectancy.
> 
> If you want to know more email me offline and I can go in to the
> specifics.  If you are purchasing for a data center and want turn key
> then I would look into the Sun T3 or A1000 or EMC and Hitachi but be
> ready for the sticker shock.  In those environments you are definitely
> purchasing a "system" but it all depends on your expectations and
> requirements.
> 
> Hope I helped, 
> John 
> 
> Links are http://www.adjile.com <http://www.adjile.com>  for the racks
> and http://www.digidata.com <http://www.digidata.com>  for our
> controller. 
> 

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