Adam Goryachev wrote at about 16:08:56 +1000 on Wednesday, April 27, 2011: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 27/04/11 15:44, Jeffrey J. Kosowsky wrote: > > Les Mikesell wrote at about 12:08:22 -0500 on Tuesday, April 26, > > 2011: > >> On 4/26/2011 11:38 AM, Michael Conner wrote: > >>> However, another idea intrigued me that I saw in an earlier > >>> posting. Someone used a RAID 1 setup but only put in the second > >>> disk periodically, then removed it for offsite storage. I have > >>> three 2T drives, so was considering something similar where I > >>> would keep a normal 2-disk RAID 1 setup but periodically remove > >>> one disk and replace it with a prior offsite disk. > >> It is working for me, but I use a 3-member RAID1 where 2 are always > >> connected and the 3rd is rotated out periodically. This isn't > >> really necessary but when I was first trying it with one internal, > >> one external drive the internal one failed, corrupting the attached > >> external, and it was something of a hassle to rebuild from the > >> remaining offsite external. > > I did it that way where the 3rd 'backup' drive was mounted via USB > > and had a *catastrophic* failure where something went wrong with the > > 3rd drive causing all three RAID1 members to become corrupted. I'm > > not sure exactly what but I ended up losing 2 years of backups. > > I suppose everyone has had their own experience with all these things, > but at the end of the day, this is a pure risk/benefit analysis > > > I think a safer alternative would be to do what the OP proposes -- > > that way you always have one safe copy not part of the RAID in case > > something messes up.... > > In other words, you are increasing the risk of your one remaining HDD to > fail during the time that you are syncing the latest removable drive you > just plugged in. You are potentially decreasing your risk of corrupting > your RAID array due to some unknown hardware issue with a previously > used USB HDD. >
But you still have a removed spare that was up to date as of the time you removed it just prior to inserting your backup drive. So, at most you lost a few hours of a concurrently running backuppc process and if you halted backuppc prior to synching (as per Les's approach -- which is a good idea to prevent disk thrashing anyway) then you haven't lost anything, assuming you have nothing else running on that disk. > As opposed to decreasing your risk to a single disk failure during a > RAID1 resync (when adding the third disk), and increasing the risk of > array corruption due to some weird code problem that you may have > experienced some time in the past... > > Not to minimise the issues you had, just wanted to remind everyone to > properly analyse the risks with the different options they select. I still think that losing all 3 (which however unlikely is still possible) is way, way, way, worse than potentially losing 1-2 out of 3 and still having a spare to recover (carefully) from. And my case can occur if you lose a disk controller or if there is a transient or if you do something stupid and overwrite the disk, etc... ------------------------------------------------------------------------------ WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/
