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From: Stan Hoeppner on 29 Apr 2010 11:30 Stephen Powell put forth on 4/29/2010 8:50 AM: > I agree with John. Stan must hobnob with an elite crowd. Not really. A computer educated crowd maybe, but by no means elite for most definitions of elite. > I don't > have a UPS at home either, and I don't know anyone that does. Be the first. Even something like this will get you through browns and sags without a burb from the PC, and will give you 5-20 minutes to do a proper shutdown with an average mini tower in the case of total outages due to the occasional storm or line crew replacing a transformer, etc. Less than $50 at WorstBuy: http://www.bestbuy.com/site/CyberPower+-+425VA+SL-Series+Battery+Back-Up+System/6201585.p?id=1069297060711&skuId=6201585 A better choice IMO would be something like this: http://www.bestbuy.com/site/APC+-+900VA+Battery+Back-Up+System/7842588.p?id=1142298456537&skuId=7842588 Provides surge protection for PC, dsl modem, coax; long battery runtime for a single home PC. Keeps the cordless phone base working during a storm along with a desk lamp so you're not in total darkness. They're great for the living room home theater system too. Allows you to watch the local weather during a storm when the power is out. > I do have one at work, but even there most desktop systems aren't > on it. The only reason that my desktop system uses the UPS is that > my cubicle is on raised floor inside the computer room and I > connected it myself. Most desktop users, even at the office, are not > so privileged. And my employer is a very big entity, financially. > It's not a small business. In the U.S. most business facilities have more stable power than residential areas. Most offices have transformers inside the building and buried cable to the building, unlike residential which, if not fairly new, has all above ground cabling and multiple houses on one transformer up on a power pole. The latter is a magnet for falling tree limbs due to wind in the summer and ice in the winter. Most offices don't suffer from browns and sags due to having dedicated transformers. Usually when office power goes out it's due to a major component failure at a substation or an overhead line somewhere in between that got clipped by a boom truck or the like. In short, office desktops usually don't need a UPS, especially if user data is stored on network shares on UPS backed servers. If power goes out it just garbles local temp files--unless it's a Windows PC and the registry was held open, as it usually is, even though it's not supposed to be... Anyway, the way I've always looked at the residential side of the UPS debate is to ask myself this question: Is it worth spending $100 to surge and power backup protect my $1000 PC and printer? For me that answer is an emphatic yes. -- Stan -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/4BD9A53C.50503(a)hardwarefreak.com
From: Monique Y. Mudama on 29 Apr 2010 12:10 On Thu, Apr 29 at 9:50, Stephen Powell penned: > > I agree with John. Stan must hobnob with an elite crowd. I don't > have a UPS at home either, and I don't know anyone that does. I do > have one at work, but even there most desktop systems aren't on it. > The only reason that my desktop system uses the UPS is that my > cubicle is on raised floor inside the computer room and I connected > it myself. Most desktop users, even at the office, are not so > privileged. And my employer is a very big entity, financially. > It's not a small business. I don't have one on my home workstation - I do on the server, and I keep anything important on it. I've also found that UPSes can fail eventually, and you might not know until the brown-out from which it doesn't protect you. I use ext3 on the server, which has fine erformance for my needs. I use the OS Which Must Not Be Named on my workstation. (I don't have a good reason not to have a UPS on my workstation - basically laziness.) As far as I know, no one at my mid-sized company has a UPS on his or her workstation. The expectation, again, is that important data goes on the fileserver, although for various reasons that expectation is not always correct. We do have the option of requesting backups for particular directories on our workstations, but I think they're nightly at best. I've actually asked about getting a UPS here and there, but given that no one else has one and that we rarely get brownouts, let alone blackouts, I haven't pushed the question. I do see a lot of non-techie people using laptops as their only computer; none of those people run linux or would recognize the term "filesystem." Among the techie people I know (in the US, so relatively privileged), very few use a laptop as their primary computer; it's usually a supplement to a beefier desktop machine. But regardless, this is back to one of those eternal tradeoffs - performance vs. data integrity. I see no reason I shouldn't use a UPS *and* a journalling filesystem when the performance of that filesystem is adequate for my needs. -- monique -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/20100429161607.GG25336(a)mail.bounceswoosh.org
From: Monique Y. Mudama on 29 Apr 2010 12:20 On Thu, Apr 29 at 10:26, Stan Hoeppner penned: > > In the U.S. most business facilities have more stable power than > residential areas. Probably true, but I've been living in my house maybe two years longer than I've been in this office, and I've had fewer power problems at home than at work. To be fair, there haven't been many in either case. So as always, YMMV. -- monique -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/20100429162059.GH25336(a)mail.bounceswoosh.org
From: thib on 29 Apr 2010 14:50 Rob Owens wrote: > The resilience is due to the way the journal is written, if I > understand correctly. Maybe somebody on this list who understands it > better can confirm or deny. There is a journal_data_writeback option > for ext3 which will speed up writes to the filesystem, but reduce its > resilience to power loss. With this option enabled, I recall reading > that the ext3 benchmarks are pretty similar to XFS. Yep. As always, LWN probably has the best word on it [1]. Short answer: ext3 is outdated, ext4 is current and can still be configured to get the same "better data resilience" without losing all its benefits. XFS should also be able to do so. Criticising ext4 for data resilience "problems" and praising XFS is a fallacy, both go in the same direction. Now the debate is around the default configuration of modern filesystems (basically performance vs safety). As YMMVVM (very much), one should probably just ignore the debate, take 30m to learn about the issue, and configure his filesystem properly. Well, opinions. ;-) For stable users using ext3, writeback can theoretically offer better throughput, as it doesn't force data to be be pushed on the platters before the metadata has been committed to the journal. It still keeps the filesystem consistent (the only thing a journal is supposed to do), but the risk of corrupting the data is greater. I, personally, don't seek to minimize that risk, I want it to be zero -- no filesystem can help here, and no filesystem will ever do. That's one reason why I don't like to see ext3 recommended for its data resilience: it gives the user the illusion of safety. Of course, it still makes sense to minimize the risk in certain scenarios where it can't be eliminated; but again, modern filesystems can be configured to do so. -thib [1] http://lwn.net/Articles/322823/ -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/4BD9D34C.1010301(a)stammed.net
From: Kevin Ross on 29 Apr 2010 15:00
> From: Boyd Stephen Smith Jr. [mailto:bss(a)iguanasuicide.net] > Sent: Thursday, April 29, 2010 7:20 AM > > Both XFS and Ext3/4 recover through journal replay, and it is usually > enough. Rarely, a manual filesystem check will be required, and xfs_check > is usually much faster than fsck.ext3 or even fsck.ext4. They only journal filesystem metadata, not the file data iself. If changes to a file haven't been flushed to disk before the power goes out, you'll end up with a perfectly consistent filesystem (thanks to the journal), but with a file or two (or more) with garbage in it. This is why at the beginning of this thread I recommended a filesystem that uses copy-on-write and preferably checksums your data. However, I don't follow my own advice, probably because I've been using XFS for so long (since 2.4 kernel when you had to download the patches from SGI). I personally haven't had a problem with data loss from power outage as a result of XFS corrupting my files. I believe this is because if a regular file (not a database) is in the process of being written when the power goes out, even if every write is synced to disk, unless whatever was writing to it has finished writing, then the contents of the file are invalid anyway, and no filesystem will protect you from that. For example, if my MythTV backend is recording a TV show and the power goes out in the middle of the recording, I will delete it and let MythTV re-record at a later date. It makes no difference if every byte in that file is correct or not up to the point of the power failure. The window of failure is when the process doing the writing closes the file, and if the power now goes out before everything is synced to disk, then you will have a corrupted file that otherwise wouldn't have been. BTW, regarding UPS's. The number of times my computer was improperly shut down as a result of a power outage is far less than the number of times other problems have caused improper shutdowns: e.g. hardware failures such as a power supply going bad, system overheating, kernel crashes, or other system lockups that require you to hit the reset button. -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org Archive: http://lists.debian.org/007201cae7cd$3af7a2e0$b0e6e8a0$@net |