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Which RAID for a Personal Fileserver?
Dredd2Kad asks: "I'm tired of HD failures. I've suffered through a few of them. Even with backups, they are still a pain to recover from. I've got all fairly inexpensive but reliable hardware picked out, but I'm just not sure which RAID level to implement. My goals are to build a file server that can live through a drive failure with no loss of data, and will be easy to rebuild. Ideally, in the event of a failure, I'd just like to remove the bad hard drive and install a new one and be done with it. Is this possible? How many drives to I need to get this done, 2,4 or 5? What size should they be? I know when you implement RAID, your usable drive space is N% of the total drive space depending on the RAID level."
For personal use, a two-drive RAID 1 is probably the easiest way to go, and involves the fewest drives, but loses the most space (half). Raid 5 is the standard, but the hardware is more expensive and it involves at least one additional drive.
For simplicity and low expense, even though you lose a full drive worth of capacity, go with RAID 1.
You might want to read The Tech Report's recent article mentioned on Slashdot if you haven't already.
That what was all this school was for... to teach us how to solve our own problems. -- janeowit
RAID 0, you need a hero,
RAID 1, is equally fun,
but RAID 5 keeps you alive!
stuff |
Try RAID 5 or RAID 10 (not to be confused with RAID 0+1). This site has a nice overview of all the RAID options. And, of course, Wikipedia has some info.
Quick overview:
RAID 5 - Requires at least 3 HDs (many times implemented with 5 - can be used with up to 24 I believe). Data is not mirrored but can be reconstructed after drive failure using the remaining disks and the parity data (very similiar to how PAR files can reconstruct damaged/missing RAR files for the Newsgroup pirates out there). % of total space available dependent on number of drives used.
RAID 10 - High performance, but expensive. You get ~50% of the total HD space as it is fully mirrored. So, 1 TB total disk space nets you 500 GB total storage space. Your data is mirrored so if one drive fails you do not lose everything. However, if you experience multiple drive failure you can be in big trouble.
Casual Games/Downloads
Whatever you do, never have more than one disk on an ide channel. Only one disk per channel can be written to at the same time, so you will get absolutely horrible performance if you get more than one hd per channel. If possible, get an ide raid card (if you can afford it) or a SATA card/mobo and drives, which dont have this problem
95% of all computer errors occur between chair and keyboard (TM)
I went through this last year and here's what I came up with for the best benefit to cost ratio with the lowest hassle. In short, take an old PC and put a four channel raid controller card in it to do RAID 5. Add a big extra fan for safety and you're done.
Here's what I came up with: Total cost about $1200 (probably less by now).
0) Red Hat Linux, ext3 filesystem.
1) 3Ware Escalade 7506-4LP card (64 bit card, but fits in 32bit slot)
2) 4x 250Gb Western Digital drives
3) Big fan.
At RAID 5 This yields 750gigs (715Gb after crappy GB conversion).
The 3Ware software has a nice web monitor interface and does daily or weekly integrity checks. It emails me if there is a problem - I did have one drive die already and replaced it easily.
Pat Niemeyer
Author of Learning Java, O'Reilly & Associates
Another missed opportunity to use the internet's, uh, hottest new acronym: FGI.
Dear Slashdot,
which is better, SCSI or IDE?
Googleless in VA
A quick note - if you re-initialize the RAID, it will erase everything you have. You should 'rebuild' the drive, unless you have a hot-swap, in which case you just take out the bad drive, pop in the good one, and ur good to go.
Have you thought about software RAID? Before everyone jumps down my throat, I realize that it's slower than hardware RAID...but, here is my rationale for using it:
1) You don't need drives that are the same size.
I've done hardware RAID, had a drive fail 2 years down the road and not been able to find an 18GB SCSI drive to re-insert to the array. That has the potential to jack your entire array. With software RAID, you buy a 36G drive, partition it so that 1 partition fits your array, and off you go
2) It's a personal file server, so speed is less important than cost (i'm guessing). With software RAID you can mix all sorts of wonderous things together. IDE drives from the basement, SCSI-320 drives you stole from work and nearly everything in between. It's for flexible, and has no associated controller cost.
3) It's easy as heck. You can configure it in Disk Druid/fdisk, and it works quite easily in any major distribution (I've done it in Slack, Debian, RH, Fedora and Mandrake).
The major downside is that you cannot (as least I don't know how to) hot-swap drives. But again, this is a personal file server. Spend your money on pizza and beer, screw the SCA hot-swap drives that are going to cost you an arm and a leg.
That's just my $0.02...flame away
Werd.
You also never touched on the possibility of him having only 2 drives, in which case RAID 1 would be the way to go for data redundancy.
She loves me: 09F911029D74E35BD84156C5635688C0 She loves me not: 09F911029D74E35BD84156C5635688BF
True story...had a personal fileserver with a Promise RAID card. I got the Promise card because it was cheap and had a good rating on a couple of review sites.
What I didn't know at the time, but learned the hard way, is that Promises's RAID monitoring program "PAM" is a user-mode only application. That means that if you don't login, it doesn't run. Care to guess what happened to me?
At some point while I was gone for the weekend, I can only guess something crashed and rebooted Windows 2000. When it rebooted, I didn't have it set to automatically login (why would I? it's a server). So "PAM" wasn't running when one of the drives in the RAID 5 set failed. Maybe it even had something to do with the crash, I don't know.
Now, the point of PAM is that if a drive fails, an e-mail gets sent, in this case to my mobile phones textpage address. Since PAM wasn't running however, nothing was sent. The drive failed and, I can only guess, put off so much heat that it cooked the drive above it (why do so many cases mount hard drives horizontally above each other anyway?) and next thing I know, I can't login to my server from where I'm staying. I call a family member with a key to come by and they are unable to restart the server. It wasn't until I came home and read the BIOS messages that I understood why. Everything gone.
I had a lot of stuff on CDR, but let me tell you, I was plenty outraged that Promise could design something so utterly stupid as a monitoring utility that doesn't know how to run as a service. Even to this day, PAM still will only run as a user-mode program, and even worse, you actually have to login to the program now to start it, which can't be scripted.
F Promise. Only a complete and utter fool would be stupid enough to buy any of their products. May they rot in that special place reserved for child molesters. (Yes, I'm still bitter about it)
- JoeShmoe
.
-- I wonder which will go down in history as the bigger failure: the War on Drugs or the War on Filesharing
Don't get too fancy with yourself on this one...
You definitely don't need any type of RAID solution because it doesn't offer you what you really need. You say you want RAID, but what you really want is backup.
All RAID solution deal with disaster recovery, but they don't deal with the situation where you accidentally rm -rf a directory that you wanted. If you mirror or RAID 5 your drives, you're still hosed because both drives will delete the files. In the end, this is more important and much more convenient.
Instead, go with a better approach which is copy or tar your files every night (or every week) to a backup drive, preferably over the network on a completely different machine. This will prevent the problem of a power surge or accidental shutoff from corrupting both drives at the same time.
there are two kinds of people: those who have had hard drive failures, and those that will have hard drive failures. i don't care if jesus h fucking christ himself blessed your hard drives.
I suggest looking at getting reliable drives before looking at a RAID solution.
and, if the poster is looking for the more-realtime-than-backup-restore reliability as he indicated, i suggest he look at raid BEFORE looking at drive quality.
the name of the game is redundancy. a RAID array of cheap drives (let's remember that it stands for Redundant Array of Inexpensive Disks) *is* more likely to have a single hard drive failure - but it's recoverable. however, it's far less likely to have multiple, simultaneous drive failures on the same day (unrecoverable) than your one, expensive, better-quality hard drive is likely to have a single failure - which is unrecoverable.
pr0n - keeping monitor glass spotless since 1981.
I've run software RAID-5 on Linux for several years on two of my home fileservers.
The only problem I ever encountered were hardware failures (Promise *ack* *spit* PCI IDE cards) and one drive failure. Performance is not really an issue for home use; I can easily saturate my 100Mbps network card.
My Fileserver: AMD Duron 1300MHz, 768MB RAM
This device was built from 4x 160GB 7200rpm SW RAID-5 for online storage (including all of my digital photos, and my collection of CD's ripped to MP3).
For backup I have an old Celeron 433, 512MB RAM box with 4x 120GB 5400rpm SW RAID-5
The main fileserver is rsynced to the backup server once a week. CPU on the backup server is a bottleneck; the Celeron is a bit underpowered for rsync, but it works ;)
My $0.02:
- Software RAID is perfectly usable, especially for typical home use. Performance is adequate.
- With RAID-5 you "lose" only one disk to parity so it is quite cheap to build
- Yes, I'd really like a 3Ware Escalade but if the card fails I need to get a new one pronto; software RAID sets can be migrated to most PCs.
-- Gxis! Ed.
I have just finished doing this exact thing.
;)
;)
I basically built a box to do nothing other than fileserv. I put together a nice simple old PC (550mhz with 256 meg of ram) and mounted it in an old rack mount case I had lying round.
It's running debian with 2.4.26.
I'm running software raid and installed 2 x 2 interface IDE cards.
I threw in 6 seagate 120 gig drives (the ones with the 8 meg cache) and ran raid5 across 5 of them and a hot spare to rebuild the raid should a drvie fail. Each drive has it's own IDE channel to prevent channel faliure from screwing my raid.
I'm using ext3 as the filesystem and wrote my own little raid mon script that SMS's me should a drive fail and alarms locally.
This setup has been rock steady and gives me 460 (ish) gig of usable space after formatting.
For added peice of mind the machine is plugged into a UPS that is connected to the machine via Serial. If the UPS kicks in it shuts the machine down properly after sending an alarm SMS (the DSL and switch are also on the UPS) (yes I'm a paranoid freak)
This makes a perfectly good media and file server and I've had no problem with it in the few months I've had it.
I also reccomend setting the spin down time onm the drives manually with hdparm. It was getting awfully warm in the box till I turned that on on the seagates. Modern drives are rather hot.
I have the whole thing mounted via SMB on my other boxes around the house and it's fast,(gig ethernet) reliable and easy.
Tho do remember that no amount of raiding will save you if you lose 2 drives through some horrible freak of badness, and no raid level is going to protect you from a house fire. Hence mine also rsyncs all my absoloutely vital files (scanned family photos and docs) offsite to a file storage site every night at 2am so as not to chew my bandwidth dduring usable times. Don't forget the only truely secure data is that which is backed up.. and offsite.... twice.