Anyone have RAID setups?

[zCypher]

Hello,

In my temptation to consider an SSD for boot + SATA for storage solution, I wonder if it might also be worthwhile to consider a SATA in RAID type setup. If you have one or have had one in the past, maybe you can share your experience.

I want the snappiness but also want the reliability/backup aspects. I'm sure if I go SSD+Sata, I will have a really snappy system but what happens in the event of a failure? Either I am making regular backups to another drive, or I risk losing data.

I'm not all too familiar with RAID but I'm under the impression you can set it up in such a way that uses striping and mirroring. Is this correct?

What do you think? I'm sure the RAID setup can come out a bit more costly if you need to buy a controller for it, but I am seeing WD Blacks with 64MB cache at $85. At this price, it's hard not to consider putting them in RAID, in light of how pleased I am with my single WD Black at the moment.

 

[Jamsan]

I use an SSD for boot drive and 4 1 TB drives in RAID 10 for storage. You lose half your usable space in RAID 10, but it's great for performance and reliability. In a 4 drive array, 2 of the drives are mirrored and then striped to the other set of 2 drives (mirrored also). This allows you to lose 1 in each mirror and still continue to run. If you lose 2 drives in any single mirror, then you'll be SOL.

RAID 01 (0+1) also has the same characteristics, but is less fault tolerant. The drives are first striped then mirrored. Losing a drive in each set causes the entire array to fail.

Store all data on the RAID array (with another backup in case the entire PC goes kapoof or stolen, etc). and then taken images of the main boot drive so you can restore quickly with all drivers, applications, etc. installed.

 

[Seero]

I have several raid setups, both hdd and ssd.

Raid 0 means splitting data thoughout drives, if 1 drive dies, all data is more or less loss.

Raid 1 means mirror/clone, as long as there is 1 drive that is still alive, all data is secured.

Raid 5 is a bit more complicated. Say you have n drives, the capacity is n-1 drives. If anyone drive dies, data of that drive can be reconstructed.

Performance:
With HDD, performance don't scale perfectly, and access time decreases as the number of drive increases. Roughly speaking, 50% performance increase of the slowest drive per additional drive until it hits the limiation of the controller.

Every performance aspect is bounded by the slowest drive in the raid, it is a good idea to use the same brand/model/size to raid.

Size:
raid0 = perfect scaling.
raid1 = no scaling.
raid5 = N-1 scaling.

Reliability:
raid0 = let say there is a 5% chance of a drive to die after 5 years of use. The chance of dying of a raid0 of 6 drives is 6x5%=30% in 5 years.
raid1 = using the numbers above, the chance of losing data is 5%^6 = 0.0000015625%. However, that is assuming that the cause of the death of drives are completely independent. Say, for example, that thurder strikes the power line, and therefore frying everything inside the house, raid1 ain't going to protect data.
raid5 = 1 fault drive tolerance.

SSD :
performance:
almost perfect scaling, and access time doesn't goes up as drive increases. However, SSD has its own performance issues and the common solution nowaday is trim, yet trim on raid is not supported, it must rely on garbage collection.

size:
same as hdd

reliability:
Unlike HDD, there is no disk, so recovering is almost impossible shall a drive dies. The original SSD design had a wear and tear leveling build-in, but recently, people decided to ditch wear and tear leveling for performance, therefore making it more unreliable and unrecoverable. Otherwise, same as HDD.

Controller:
Most mobo comes with a onboard raid controller which is good for HDD raid, but if you are going to raid high-end SSD, you will probably need a PCIe 8x controller as the onboard controller will become a bottleneck.
Note that onboard raid controller requires CPU to work, meaning that it not only use CPU, but i/o towards CPU. This itself will become new bottleneck depending on the task you are doing. If you are gaming, you may find the loading time decrease but slightly lower FPS with onboard raid HDDs.

Others:
In you are gaming, a single SSD > raid SSD > raid HDD.
For multi-media storage, instead of raiding HDD, you can simply use symbolic link to create a single drive, and SSD is too expensive for that purpose.
For work, you can either store files on HDD, or have a scheduled backup to HDD everynight.
If you want size, buy a big HDD. If you want speed, buy a SSD. If you want both, buy both. Trying to create a raid with HDD to compete with a SSD is pointless. Trust me, I tried. I have 4x Western Digital Raptor 150GB@raid0, but a single vortex beats it in terms of gaming or work. Now it becomes a big garbage can that it is better off unraiding them.

 

[Emulex]

if you can't afford datacenter grade gear - skip raid-1 and raid-5 just use raid-0 for speed (and backup) . seriously. backup backup backup.

raid-5 is a joke even in datacenter without a hot spare (which is essentially raid-6). double drive failures or chassis failures happen more often than not. sometimes by stupidity. oops pulled the wrong drive out on amber light. thank god i had raid-10 (which is a bunch of raid-1 pairs striped with raid-0).

 

[nanaki333]

i've been using dual intel SSDs for over a year in raid0 and never had a failure. in the event of a single drive failing though, it's gone.

 

[veri745]

I had a raid 0 system drive + raid 1 for storage setup for a while. Finally ditched it in favor of SSD+SATA with a HTPC backup.

In my opinion, SATA RAID for a desktop system just wasn't worth the hassle.

 

[dac7nco]

RAID is for uptime, not storage. If you just want a huge storage pool, use ZFS. Keep a RAID-10 for storage on your workstation, a stand-alone backup server for archives, iSCSI targets for the backup server, physical HD backups in a fire safe, physical HD backups in another location, online backups at Carbonite, backups in the trunk of your car, under your desk at work, in your mom's garden shed and under the sink at your girlfriend's house.

I spend a LOT of money on storage... You WILL eventually lose your data, and become a paranoid morning drinker like me.

Daimon

 

[Emulex]

I think managing storage does make you stupid paranoid. Having seen several multiple drive failures (saved by raid-10) the odds are better to win the lottery iirc. isht like this makes you paranoid. it also saves your butt when things really go awry. we wen't through dark passages with ultra-scsi when they tried to make things go too fast - and the whole sata-raid wtf are they thinking. thank god SAS has returned stability and will lead and replace even FC drives with their terrific dual ported yummy-ness

and good riddance to tape drives. man. i hated quantum autoloaders

 

[dac7nco]

Emulex, tape is still kicking - a 1.5TB Ultrium 5 tape is price-competitive with SATA hard drives, and is less prone to shock damage. The drives are still nightmarishly expensive, though, and autoloaders still suck.

Daimon

 

[Doggiedog]

I've had a RAID0 setup for several years. I have had several HDD failures. That's why I keep things I don't really care about on the drives. I mainly use it for uncompressing RAR files and rejoining PAR files. RAID for my purposes seriously is 5x faster than plain old SATA.

 

[zCypher]

Wow thanks for all the informative replies! Sounds like it could get complicated. I want to find a happy medium. Anything that's important to me I keep more than one copy in more than one location. I haven't historically bothered to make images of my system, but I'd like to play with that so that if I do have a bad crash I can just reload an image and poof, everything's back.

The reason I got interested in RAID was because of the low cost of SATA3 drives with 64MB cache. I've seen some WD black under $60, hard to argue with that. I would love an SSD, but where can you find a good cheap one?

 

[pjkenned]

One thought is to get a SSD as a boot drive, then have a local RAID 1 array for local storage/ backup. For $160 these days you get 2x 2TB drives and your downtime due to disk failures will nosedive. Even if the SSD dies, restoring from local backups is pretty quick.

Network backup is always good too.

 

[HappyCracker]

It really doesn't need to be complicated, it just depends on what your needs are. Something to note is, RAID-(1/10/5/whatever) is not a backup. If the OS decides to write a bad bit, all of the data can go south with it. RAID (non level zero) really exists to protect you in the event of drive failure.

My personal setup consists of the OS (Linux) on one drive; in the event it dies, I'll just rebuild it, no worries. I then have, two dmraid RAID-1 arrays in the same machine exported as iSCSI drives using IETD to a Windows machine that treats them like local drives. I've had drives come and go from the array with no issues. It's a setup that fits my needs and I feel it's cost-effective. Setting up some way to monitor the health of the arrays is important; I get nightly status e-mails to make sure alerting is working and health checks every 20 minutes which would e-mail every 20 minutes in the event of a failure.

 

[zCypher]

Exactly, good point about the needs. This is why for now, I've ordered another TB Black to go with the current one I have in here. My MSI board supports, I believe, 4 SATA connections. I don't have massive amounts of critical data right now so I feel as long as I have copies of my important stuff in various places I'm ok.

How reliable are RAID controllers? Also, I'm wondering how tangible the performance benefits of striping are in the context of basic usage (web/IM/light gaming).

 

[dac7nco]

zCypher,

To answer, RAID controllers are very reliable, but they can die, and then you can't use your hypothetical RAID-6 until you replace the controller with the same model. You also need a battery backup for the memory on the controller to keep cached writes in case of a power failure - the batteries alone are >$100. You can operate the controller without a battery, but with much reduced performance.

To your unanswered question, you don't need - OR WANT - RAID. Get a dual-port eSATA card and external drives when you run out of internal ports. You can make incremental backups of your treasured media using freeware, such as Karen's Replicator.

http://www.google.com/url?sa=t&sour...xqTSBQ&usg=AFQjCNGdRZx6t-bCxTNfI6Buy7D-4t8HNg

Daimon

 

[zCypher]

zCypher,

To answer, RAID controllers are very reliable, but they can die, and then you can't use your hypothetical RAID-6 until you replace the controller with the same model. You also need a battery backup for the memory on the controller to keep cached writes in case of a power failure - the batteries alone are >$100. You can operate the controller without a battery, but with much reduced performance.

To your unanswered question, you don't need - OR WANT - RAID. Get a dual-port eSATA card and external drives when you run out of internal ports. You can make incremental backups of your treasured media using freeware, such as Karen's Replicator.

http://www.google.com/url?sa=t&sour...xqTSBQ&usg=AFQjCNGdRZx6t-bCxTNfI6Buy7D-4t8HNg

Daimon

Thank you. Looks like the best option at this point is to get an SSD as boot drive and keep two TB Blacks (one for backup).

 

[Emulex]

i think alot of people get their e-peen on when they said man i got 4 drive raid-5 at home. i understand that. try it once. but just heed our warnings. its not cheap nor the best solution. its a BURDEN for consumer. It's a requirement (Raid) for business.

or get a drobo or qnap - they have magic drivers that can use all types of drives - at once.

 

[zCypher]

i think alot of people get their e-peen on when they said man i got 4 drive raid-5 at home. i understand that. try it once. but just heed our warnings. its not cheap nor the best solution. its a BURDEN for consumer. It's a requirement (Raid) for business.

or get a drobo or qnap - they have magic drivers that can use all types of drives - at once.

I was curious about it, as I'd heard the term (RAID) over the years but never really understood what it was all about. This thread definitely helped me understand.

 

[bigboxes]

RAID is not a backup. Raid is for performance and/or uptime. You want RAID performance just use a single SSD. I use Acronis TrueImage and save a make a complete image after my initial build. After that I just make sure to back up my data separately from the image.

 

[dac7nco]

In the early 90s when RAID first gained mass popularity, hardware controllers were neccessary for almost ANY form of RAID, as the CPUs of the time were way too slow to handle parity calculations... and do absolutely anything else. These early RAIDs were kept far away from most home users due to their specialized, UNIX-only hardware and the fact that a bunch of 207MB SCSI-2 drives cost as much as a Toyota. Around 2005, when IPC grew to the point that "software" RAID using idle CPU cycles became possible, chipset manufacturers fount a new, BAD way to let home users use all their new SATA connectors at once. The vast majority think it's safe... If your 4-drive RAID-5 Array of 2TB disks fails while you are asleep, even if you wake up and replace the fragged drive, the odds are pretty good that another drive will fail during the LONG rebuild process, and you will never see your 6TB of meat-flicks again. RAID-6 on is almost as dangerous, as it drives users to create much larger arrays, because the 2-drive safety net SEEMS bigger.

One other, often overlooked drawback or RAID, is that it usually - goddamn near ALWAYS - fails when you've just managed to fill it with far more data than you have available for backup space.

I'd wager that spending the cash for a huge I/O pipe to your house and an enormous online backup plan would cost less than upkeep (and your stress) on a few hardware RAID arrays, and that Amazon/Carbonite... etcetera are less likely to lose your data than you are.

Daimon

 

[Emulex]

i heard tape backups in the back of a station wagon are the fastest way to transport data these days

 

[dac7nco]

I wasn't joking about keeping backups in the trunk of a car!

 

[martixy]

I would have imagined that RAID5 and RAID6 are the most commonly used...
Seriously - what are the chances that a second/third drive will fail for an independent reason within the timespan it takes to rebuild the RAID(too lazy to calc right now)?

My current setup is 2 WD7502ABYS drives in RAID0, works well enough for me. I do have another 400GB drive, but it doesn't factor in the RAID setup.

My ideal storage solution would be a 3 tier system:
1 120-240gig SSD boot/work drive;
the 2 disks above in RAID0 again for working storage;
1-2 2TB backup/multimedia/streaming drives;
Fairly affordable.

 

[dac7nco]

martixy,

the time to rebuild an array is dependent upon the size of the array - the larger the array (especially with RAID-5), the more likely a rebuild will fail. RAID wasn't designed for drives with the capacity we have now, and RAID-5 with consumer disks fails at the rate of Murphy's Law. The main problem I have with consumer RAID is that it encourages users to create storage pools larger than they can financially support.

Your 3-tiered storage is the correct workstation setup.
Edit: Fast HDs in RAID-0/10 for work storage - SSDs are unnecessary for work storage, as all you need are big sequential writes.

Murphy was an optimist.

Daimon

 

[martixy]

Don't you mean Moore?

Murphy's version would go something like this: If you need 2 to fail, when 1 fails, a second will fail before you replace the first just to spite you.

I've also had some experience with copying entire drives of data so you just need to tell me if there is overhead to raid rebuilding and what are these capacities that RAID5 wasn't designed for?