Hi,
I find that I am not really in a position to give any authoritive comments
about this.
We did have a visit from StorageTek who flog this stuff.
What is SAN (for those who might want a thumbnail of what it is about)
SAN is a way of delivering access to disk space across what is called Fibre
Channel. Fibre Channel, is an evolving standard as I understand it, it is a
point to point connection involving optical cables (there is a copper
standard, however) and hubs (similar to switched ethernet hubs). The address
space is 7 bits or 126 devices. It can accomodate redundant connections
between devices, if you want to fatten up certain pipes (ie connections).
The disk space is usually handled as a huge array that maybe raided or
mirrored, and the array controller allows you to carve up the disk space and
allocate it to particular clients. Delivery of information over the FC is
supposed to be of the order of 100mbytes a second (not sure I have that
figure correct, anyway its supposed to be fast, faster than ultra scsi-2). A
fair amount of redundancy is built into arrays and array controllers.
StorageTek sell the hubs, the FC cards for clients, and the disk arrays and
controllers. They profess that their equipments will work with most vendors
and will interconnect to most OSs (NT, AIX, HPUX, etc). However they
indicated that Compaq seems to be rolling its own, and to some extent their
equipment does not work over Tru64. Anyway, unless you are thinking big
amounts of storage, I guess the next step up from a terabyte, then this is
probably the solution for you, but you have to sort out what does and
doesn't work with Compaq. Initial costs seem to be fairly high, you have to
fork out for
(a) FC cards for clients (around $2k-3kAus)
(b) optical cabling,
(c) FC hubs ($30-40kAus),
(d) disk arrays and controllers (the sky maybe the limit)
Other than that, I would suggest you scout around the internet.
I had some replies from:
(a) Scooter Morris [scooter_at_gene.COM]
It sounds to me like you may be confusing SAN (Storage Attached Network)
and NAS (Network Attached Storage). SAN's almost always involve some sort
of FibreChannel fabric and use FibreChannel Host Bus Adaptors (HBAs) to get
direct access to the storage. NAS generally uses some network protocol
(NFS,
CIFS/SMB, and more recently ISCSI) to access storage over a TCP/IP network.
If you are thinking of building a NAS, then a DS10 with SAMBA will make a
pretty good combination. Recognize that (at least at this point) NAS is a
lower
(b) Clegg, Larry [Larry_Clegg_at_intuit.com]
The SAN technology offers you greater flexibility and usually speed. Once
you get your fiber setup then you can add 100s of more disks, tape, etc.
without any downtime. That's the way I'd go.
(c) O'Brien, Pat [pobrien_at_mitidata.com]
they are both great in thier own right, but apples & grapefruits compared to
each other. All 3-channel raids I ahve worked with have a 32 gb limit to
logical volume size and were next to imposible to up and move to another
system. Now the sans that I am rolling out have hundreds of gb per logical
volume, and are quite easy to umount and remount to another system. this is
scsi over fiber and much faster than a nfs mount. Now I have not touched a
3-channel raid for many months, but shoould the right oppertunity arise, I
might again, but I would be very carefull as 5.X has limited the flavours to
which it will play with. And then oh 5.1 makes sans even easier. then
after reviewing technical needs of the deployment look at cheap vs not so
cheap.
(d) Dan Harrington [dan.harrington_at_av.com]
I'm not sure that a SAN would offer any benefits for a single system...but
after spending a year managing 24 ES40's that had only enough local disk to
hold the OS (plus swap), I'm just in awe of how *flexible* a SAN be! So
long as you don't run out of drives, it's very easy to configure and deploy
new disk units, recycle old ones, and just keep things going smoothly from
the operational side. I'm sure there was a performance penalty, but it
fell within the requirements of our application, and worked for us.
(e) Lu, Qiang [Qiang.Lu_at_compaq.com]
http://www.compaq.com/products/storageworks/san/index.html
(f) alan_at_nabeth.cxo.dec.com
The first potential benefit is volume of storage. With the
KZPCC you're relatively limited in the number of disks that
you can connect, and thus capacity. Until the DS10 runs out
of PCI slots and up to the number of KZPCCs supported on it
you can add more, but compared to what you can get with Fibre
Channel based connectivity, it is still pretty limited.
With subsystems that can actually stress the 100 MB/sec
data rate of current Fibre Channel, the KZPCC isn't likely
to have comparible performance (I don't know what it claims).
If you want to add one or more systems and build a cluster,
then the KZPCC based storage is only local to that one system.
Fibre Channel connected storage is available to all systems
on the fabric.
(g) Udo Grabowski [udo.grabowski_at_imk.fzk.de]
SAN has advantages if you connect several hosts to the same storage
system. The SAN storage is not "owned" by a host, but is an entity by
itself, which can be attached to several hosts simultanuously. It is
usually used in a clustered system.
Dennis
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Dennis Macdonell
Systems Administrator
AUSLIG
mail: PO Box 2, Belconnen, ACT 2617
email: mcdonell_at_auslig.gov.au
ph: 61 2 6201 4326
fax: 61 2 6201 4377
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Received on Mon Sep 17 2001 - 23:41:56 NZST