At 06:38 PM 06/22/2002 -0400, Steve Fulton wrote:
At 17:37 22/06/2002 -0400, geer@world.std.com wrote:
Not arguing, but the hardware cost curve for storage has a shorter halving time than the cost curve for CPU (Moore's Law) and the corresponding halving time for bandwidth is shorter still.
You've got a point. Storage is becoming less and less expensive per gigabyte, especially for IDE drives. If you're using a RAID set up, IDE doesn't cut it, SCSI is the way to go (for now). SCSI is a lot cheaper than it used to be, but it's still over $1000 for a single 70gig drive in Canada. For maximum redundancy in one rack-mount server, RAID 10 is the way to go. That means for every 1 drive, there must be an an exact duplicate. Costs can increase exponentially.
[more examples of expensiveness deleted; fibre channel, etc.] You're not making appropriate technology choices, so your costs are off by a factor of 5-10. IDE is just fine, especially in RAID configurations, because if you're making a scalable system, you can use as many spindles as you need, and you don't need to run fully mirrored systems - RAID5 is fine. Almost any technology you get can run 5MB/sec, which is T3 speeds, so that RAID5 system can keep up with an OC3 with no problem. Disk drive prices here in the US are about $1/GB for IDE. The problem is that's about 200 seconds of T3 time, so your 5 100GB drives will last about a day before you take them offline for tape backup. The real constraints become how fast you can copy to tape, i.e. how many tape drives you need to buy, and what fraction of data you keep. If it's 1%, you can afford it - adding $5/day = $150/month per T3 is just noise. Keeping 10% of the bits - $50/day = $1500/month/T3 - is a non-trivial fraction of your cost, so you have to go for tape. Fibre channels are useful for cutting-edge databases on mainframes, and have the entertaining property that they can go 10-20km, so you've got more choices for offsite backup, but GigE is fine here. Make sure you also keep a couple of legacy media devices so you can give the government the records they want in FIPS-specified formats, such as Hollerith cards and 9-track tape.....