In the office, we curr­ent­ly have about 120gb of disk that need regu­lar back­ups. We wan­ted to have a solu­ti­on that enables us to store off­si­te copies easi­ly and was­n’t too expen­si­ve. Tapes were out for hand­ling reasons – tho­se dri­ves that we were wil­ling to afford would have meant a sys­tem of cas­ca­ded incre­men­tal back­ups, making res­to­ra­ti­on of sin­gle files a tape-shuff­ling issue. DVDs don’t hold enough data and their sto­rage times are not yet ful­ly unders­tood, so that did­n’t quite sound so prac­ti­cal, either. 

In the end, we deci­ded to out­fit one of the older machi­nes around (a Pen­ti­um II) with remo­va­ble hard disks (nor­mal Wes­tern Digi­tal 160 GB dri­ves, fit­ted into run-of-the-mill alu­mi­ni­um mobi­le racks). We have two dri­ves fit­ted into a car­ria­ge, so there’s always one at home and one in the machi­ne. During the day, the appro­pria­te machi­nes copy their data onto that one volu­me over the net­work and I can take along the disk in the evening, brin­ging the other one next morning. 

Most of our machi­nes run Net­BSD so I’ll just quick­ly run down the very basic con­fi­gu­ra­ti­on, we have here, but it should also work with many other unix-like ope­ra­ting sys­tems. Ope­ra­ting sys­tem and all esen­ti­al stuff is on a disk that always remains in the back­up machi­ne, the back­up volu­me is a dri­ve off the secon­da­ry IDE controller. 

The machi­ne is only powered on when the disk is in, so there’s no cho­king on miss­ing disks – this could be avo­ided by using a hot­swap-enab­led IDE con­trol­ler, but curr­ent­ly, we don’t have that need. As soon as the disk goes in in the mor­ning, the machi­ne is powered up, boots and shares the back­up volu­me via NFS. The other machi­nes (all run­ning Net­BSD) have that volu­me in their auto­moun­ter. Scripts are star­ted that use dump(8) to copy their appro­pria­te sli­ces onto the back­up dri­ve. As soon as they’­re all finis­hed, the machi­ne powers down again, wai­ting for the dri­ve to be taken out. 

And that’s all the­re is to it!

Pri­ce of the machi­ne: prac­ti­cal­ly not­hing, we had that alre­a­dy. We even had an emp­ty 4U 19″ enclo­sure, so it’s gone into the machi­ne rack.
Pri­ce of the dri­ve enclo­sures: 25 € each, making it 50 €
Pri­ce of the hard disks we’­re using today: start­ing from 80 €
That makes our con­fi­gu­ra­ti­on total 210 €. Not bad for 160 GB of back­up storage. 

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