Originally posted by: Zepper
Short lengths of 18 ga wire can handle about 10A, so you probably don't want to run more than 6 or seven drives per branch off of the PSU to take the added startup current into consideration. Amp makes drive power connectors that you can clip right onto existing 18 ga wires (like insulation displacement connectors on drive cables.) Zippy PSUs have drive branches that are about 21" to the first connector and another 7" to the other one (only two per branch) total 28" long. Would be a good one to mod for that. You need to know the max startup current of your drives so you can judge what total amps on the 12V rail you need.
. Are you able to stagger-start your drives on initial power up like SCSI? If so, you might be able to put more than 5 or 6 per branch off the PSU. In any case, I know of no PSU that has that many drive connectors as standard equipment. With that many drives it is std. practice to use hot-swap cages that only require one or two drive power connectors per cage. If you are going cageless, you will have to do the 'Y' thing or roll your own connection solution.
. Using two PSUs is probably a good plan as buying one with the Amps you will need if all drives start up at the same time will break the bank. The $300. , 700W Zippy claims 45A@+12V and that is about what you will need (about 42 A, maybe more, just to cover the drive startup surge). While you can get two high quality PSUs with about 50A total on the +12 for under $200. Once all the drives are spun up, you'll only need 14A plus some headroom, say 20A total) to keep them going. Stagger start is a GOOD THING!
. If one PSU goes bad, you may lose your array; if one of two goes bad, you lose your array. The odds are a bit higher, but not drastic. The key is making verified backups. RAID is NOT equal to backing up - even RAID 5 - it's purpose is mainly to minimize downtime. If you plan on running w/o backups then I'll be here with the "I told you sos" and my miniature violins... 😉 You will want to put the whole thing on a stout UPS too. I seldom have any hardware problems with a machine that runs off of a quality UPS - "pity the fool" that runs without.
.bh.