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... but my PC at home has a terabyte! - Ed's journal
... but my PC at home has a terabyte!
One of the things I get from time to time, is complaints about price and availability of storage in our SAN.

We have a large storage array - some 200Tb. The cost per gig, is ... well, I haven't checked recently, but it's high. It's a lot more than you'd pay for a 500Gb SATA drive at PC world.

So every now and then we hear the 'but I could buy that way cheaper'.

And ... yes, if all you wanted was a box of bytes, you could indeed get it way cheaper.
Thing is though, and enterprise storage array, has several things that your home PC doesn't:
15K RPM fiber channel drives. They're fast data rate, and fast seek drives.
64Gb of cache. (Yes, that's not a typo. This array has MASSIVE amounts of cache)
4Gb end to end, of Fiber channel bandwidth.
No single point of failure architecture - there's at least two of everything, and it can manage concurrent activity on multiple ports/devices, and gracefully fail.
Internal bandwidth of about 128Gb/s. (Not that this is a meaningful number in real use, but everything internally is multiply cross-connected).
High performance RAID controllers, which can actaully cope with 2000 physical drives at once.

And then there's the supporting architecture:
Fiber Channel network - the SAN is a fiber optic high speed, low latency network. Those are expensive. We're talking about £1000/port kind of expensive. You'll need at least two per server, sometimes more. And then we need to extend it out, and add new switches.

Remote replication - we don't have one volume with your data. We actually have 4. We have a local replica that we use to backup. We have a remote replica that we use for disaster recovery. And we have a remote replicata that we use for backups. Oh, and we use a LOT of bandwidth to keep those remote disks in sync with your local disk.

Backups. LTO3 tapes are about £50 each. And your 'terabyte' needs backing up every day.
Network throughput to the backup server - multiple servers backing up 'a few' terabytes every day, adds up pretty quickly.

Support contract - 24/7 4 hour response isn't cheap. But that's what we get.

Host infrastructure - your server needs 2 fiber channel controllers, they're expensive. The multipathing software for them, to allow them to concurrently use multiple ports also comes with a price tag.

So yes. Your disk from PC world is cheaper, byte for byte, than our SAN storage. But y'know, garden sheds are cheaper than mansions too.
3 comments or Leave a comment
From: (Anonymous) Date: May 27th, 2008 11:50 pm (UTC) (Link)
Hell, yes. We decided against a big fibre channel box for our latest mailserver - but some pencil pusher later questioned us on our choice - according to him we could have got 20TB system for just 80K.

I wanted to see his face when he got our reply telling him that was just the
cbr_paul From: cbr_paul Date: May 29th, 2008 01:25 pm (UTC) (Link)
"garden sheds are cheaper than mansions too"
I love this line!
the_wood_gnome From: the_wood_gnome Date: May 29th, 2008 09:27 pm (UTC) (Link)
Surely it's

Portaloos are cheaper tha Superloos? ;)
3 comments or Leave a comment