From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Leslie Rhorer" Subject: RE: Is My Data DESTROYED?! Date: Sat, 24 Oct 2009 21:30:56 -0500 Message-ID: <20091025023059520.QFQH17264@cdptpa-omta04.mail.rr.com> References: <7bc80d500910241903i1c3faf48r2706d58e14a11016@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <7bc80d500910241903i1c3faf48r2706d58e14a11016@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: 'Christopher Chen' Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids > On Sat, Oct 24, 2009 at 6:52 PM, Leslie Rhorer > wrote: > >> I'm going to go on a limb here and say for anyone (with data they = want > >> to preserve), no matter what, backups make sense and are cost > >> effective. I'm going to be crazy and say that there's no reason th= at > >> someone who thinks they can afford a 8TB disk array and dual SLI v= ideo > >> cards, etc, etc, can't also consider some sort of disk or tape bac= kup. > > > > =A0 =A0 =A0 =A0I agree with the disk backup, but not the tape. > > > >> Cumbersome? Can be. But having worked with datasets and filesystem= s > > > > =A0 =A0 =A0 =A0Cumberesome, slow, kludgy, and expensive. >=20 > Well, like anything else, having a system helps. And by system I mean > a library, barcodes on all tapes, and a good tape storage system. Yes= , > it involves Humans. Well, that wasn't quite my point, but it is another aspect of the issue. > >> that run into the hundreds of terabytes, and having backed them up= to > >> tape, it makes sense. If you have something on the order of tens o= f > >> disks, sure, go ahead, take that next step and back them up somewh= ere > >> else to another set of disks. If you have more disks, seriously > >> consider tape--in terms of capacity and power consumption (and dat= a > >> integrity), tape wins. > > > > =A0 =A0 =A0 =A0Power consumption, yes. =A0Capacity is a somewhat mo= re complex > > problem, with a number of variables. =A0For speed, tapes lose > disastrously. > > For cost, hard drives win unless the array is very large. =A0For > reliability > > and availability, drives win hands down. =A0I've had quite a bit of= data > lost > > with bad tape sets, and the most persistent problems on my systems = which > do > > use tapes involve the tape drives, even sans data loss. =A0Once som= eone > wiped > > out a directory which someone up in corporate was backing up to tap= e. > =A0It > > took 3 days to recover the directory, no doubt because no one could= find > the > > tape. >=20 > I'm not so sure about the speed--you can stream 100MB/sec to a single > tape drive, and if you have multiple in a library, it just scales > horizontally. First of all, that assumes the tape is loaded and ready. It can take hours or even days to retrieve a tape and load it. Secondly, whil= e the tape can stream 100MB/sec, it isn't random access. Finding a 200 byte = file in the middle of a 1T tape backup is going to take a while. Getting it= from an online backup server takes perhaps 10ms after the admin finishes typ= ing the copy command. > But, where I was working, we were also duplicating tape sets for > offsite, which means there was two copies per backup set. >=20 > Is this expensive? You betcha! But...you know. The bad old days of DD= S > are also gone, so there's some rejoicing there. They may be for you. I have to manage over 300 of the beasts on the same number of hosts. What's worse, not only are the backups themselve= s often incompatible, the drives often can't even use the same tapes. I = have to see to it a half dozen different tape types get stocked in 75 differ= ent cities. Then I have to try to make sure the gopher in every city remem= bers to replace the tape. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html