On Mon, 2002-05-20 at 06:22, Alvin Oga wrote: > > hi ya ron > > On 19 May 2002, Ron Johnson wrote: > > > You and I must think on different scales... > > think its similar scales.. > - different ways to skin the cat... > > - a tape is 40 - 80GB.... same as disks ... nowdays disks is > always slightly higher capacity.... You're behind the curve. AIT3 and SDLT offer capacities of ~200GB per tape. > - there was a time when a single tape had more capacity than > a single disk... and better price for disk$$$/MB vs tape$$$/MB > > - in the old days... whan disks were expensive per GByte > and tapes were comparably cheaper.... tapes would be better Tape is still cheaper per gigabyte. Can you get a 220GB disk for ~90 quid? > > - any argument for number of disks is equally applicable > to number of tapes .... > - tape library vs raid ... > ( same issue here too ) > > - we had/have a bunch of Exabyte Magnum(?) drives ( $8K each ) > a few years ago ... when 20GB disks was just coming out... > but the tqpes was too slow... even with tar + buffer ... > tape cant keep up for backing up xxxGB of data > - went to disks for backup and never looked back since... You'll look back with regret when your disk-based backup system eats itself alive. Hard disks fail. Tapes might fail too, but they fail less often, and have less impact on the overall system when they do. Easier to replace, easier to obtain. If push comes to shove, I can get tapes from the local Staples. > those tapes was good for 80GB or so... > and we had 40 users at 20GB each... > > - i require 3 independent sources of backups.... 2 is minimum.... > ------------------------------------------------ > - > - offsite is not important as much as in different buildings > - > - if a build burns down in a fire... that's what monthly > backup is for.... take the disk and store it some place else ... > > --- if the disks is raid5'd ... give one disk > --- to each of the CEO/CFO/CTO/foo/bar and no one user > --- has all the data... no way for stealing corp secrets That's innovative, but impractical. > - majority of stufff i do is across the ocean ... > - > - can't go around changing tapes... :-) > - and even if the tapes was in my office... i still wont use it > - as we all step away on weeekends and holidays and sick etc... > - > - i say a tape based backup fails the day somebody forgot > - to change the tape... you lost yesterdays data > - Depends. If you run two tape drives and have a tape jockey onsite to swap the tapes, you're OK. > - out here... 50-100GB of data to play with per day per user ... > - most of the generated outputs is not backed up > since its easily regenerated by the spice programs... > > - when doing full chip layouts... we can get into 10's Terabytes > of data... most of which i claim is worthless.... > and constantly changing .. no pointto backup other than for "archive" > and the lawyers to have a running history... A terabyte is 10 AIT-3 tapes. How many disks is it? > - what cannot be lost is the schematics and simulation parameters > > all that (incremental) data is saved over 3-6 month periods... > - each user pc has about 160GB of disks > > - wondering how to backup data/service on an OC3 line now... > ( next project ... > > have fun "backing it up"... > c ya > alvin Believe me when I say that you're in a minority amongst sysadmins on this topic. > > > 30 days worth of the 155GB database that I manage, plus > > the 40GB of flat files == 5.8TB > > > > 30 days worth of the 80GB database that I manage, plus > > the 20GB of flat files == 2.4TB > > > > 30 days of the 1.5TB disk space that my co-worker manages > > plus 200GB of flat files == 57TB. > > > > That's 65.5GB of storage, or 546 120GB ATA disks. The > > cabinets, controllers & power supplies needed to run all > > those disks is _really_ expensive. (If you want them to > > be RAID5 secure, add, oh, 15% more disks, so that's 628 > > spindles!!) Yes. These are the kinds of numbers I came up with when contemplating a disk-based backup system for the system I work on which entails backing up circa 100GB a night. I need to keep long-term backups for a year, too. > > Last, but _certainly_ not least: > > If the machine gets destroyed (fire, etc), there goes a > > huge business. Can't happen? I managed an 80GB OLTP > > database in the WTC... > > > > There is NO WAY I'd allow an important production system > > without off-site tape storage. Werd to that, Ron. Peter. -- Peter Whysall peter.whysall@ntlworld.moc The TLD in my email address is sdrawkcab. Debian GNU/Linux 3.0 sid -- kernel 2.4.18
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