Is RAID 5 really a solution?

Dante_Stella

Dante_Stella

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It seems that a lot of RAID 5 solutions have been pushed onto the market - but do these really help?

I was looking at RAID units in conjunction with outfitting an iMac Retina 5K to have some kind of realistic storage. In looking at using a very big, very fast RAID box to store user profiles and about 5tb of data, I ended up with the following observations after looking hard at a Thunderbolt RAID array:

  1. The only redundant systems that don't put a huge hit on read speed are striped;
  2. Striped sets are very sensitive to drive issues (as I have learned firsthand...), and the more drives, the higher the likelihood of a failure;
  3. To overcome stripe deficiencies, you have to resort to mirroring (RAID 1+0) or parity (as in RAID 5 or 6), but either puts a big hit on read and write speeds;
  4. In a RAID 5 or 6 system, which is supposed to overcome the risks of striping, the rebuild times for data in the terabytes is monumental. It can take 36 hours to sync 3 x 3Tb drives because even the initial sync hits every block on the drive.
  5. If resynching occurs on failure, all of the drives in the array are running full tilt to reconstruct the failed drive - and in the interim, if thermal issues caused the original failure, you're inducing them again. And in RAID 5 particularly, a second drive failure takes the whole system out.
  6. Resynching a RAID also puts a days-long hit on performance.
  7. If you are not watching for a failure, and it happens, then the degraded array is running unprotected for as long as it takes you to detect and mitigate the issue.
  8. The "hot spare" concept is a great idea - except that the hot spare costs money, cuts capacity and is being cooked in the enclosure until it is called upon. At best, it is sitting still and baking; at worst, it is spinning and incurring wear and tear like the other drives.
All of this makes me wonder whether the RAID concept has outlived its usefulness when it comes to monster HDs. Maybe this was a great idea when HDs were at the 100Gb mark, but today, not so much. With huge, cheap HDs (heading toward 6tb for $200) and interfaces like Thunderbolt (which are faster than any drive that hooks up to them), it seems that you're almost better off cloning a main drive periodically and storing the copy off site. In fact, for the price of many RAID 5 units, you could make multiple off-site clones.

Am I crazy? My conclusion was to use a striped set for working files, a RAID NAS (not on all the time) to deal with backups, and a couple of clones in external housings (FW800/USB3/eSATA) for the real disasters.

Dante
 
I like to live on the edge. All of my PCs, down to my Vaio ultraportable, have main drives in RAID 0 😀

But no, I don't care for RAID 5. Disk space is dirt cheap these days. Why bother with rebuilds when you can just get two drives and double backup everything?
 
Dante_Stella said:
........Am I crazy? My conclusion was to use a striped set for working files, a RAID NAS (not on all the time) to deal with backups, and a couple of clones in external housings (FW800/USB3/eSATA) for the real disasters.

Dante
Click to expand...

Looks like a good solution to me, and is more or less what I use. No matter how great the RAID is, it can still have a fault (I lost my whole array, RAID6 QNAP which the manufacturer could not help with). Nothing beats multiple external USB3 HDs, a couple of them off-site.
 
🙂

My name was spelled this way by Germans as they read word phonetically ... Rah-ed
I ended up have Raid as my name.
 
RAID 5 is nice, but overkill, more expensive - and on the slower side. RAID 6 is a better choice if you must go this route, but many products don't offer it.

I popped a G-Tech "G-RAID Studio" on my iMac 5K. It's a RAID 1 (mirror) and offers both data redundancy and speed, without using a lot of drives. Of course, you can also set it up as RAID 0 (striped, for speed - no redundancy) or JBOD (two individual disks - again, no redundancy). Bonus - it's Thunderbolt 2. Though that speed advantage is lost on a two-drive RAID 1.
 
photomoof said:
Well sort of... but important to remember no RAID level will protect from multiple disk failures.

The more disks, the more likely there is one off-line, and then the disk array is not fully redundant.

I no longer bother but, old good tape backups are still important.

Personally I still back up individual completed works on CD. Crazy? Maybe.
Click to expand...
I have a network Drobo drive that protects from two drives going down at once. Of course, rebuild time would be long, but that is a small price to pay.
 
I'd skip the raid entirely, just use external drives in a JBOD setup for backup and automate the backup of those... So if you have an external housing, put two drives and use super duper or ccc to schedule a regular backup from the primary backup to the secondary, say once a week or every few days.

Why bother with a NAS when you're buying a desktop machine? If you install OS X server you can serve the drives you want via your imac to any other machines on the network.

With the imac, get the biggest internal ssd and keep your lightroom catalogs on it and your files on the thunderbolt jbod, performance will be fine.
 
Dante_Stella said:
... In fact, for the price of many RAID 5 units, you could make multiple off-site clones.
....
Am I crazy? ...
Dante
Click to expand...

So, facts, please.

I have about three terabytes (3TB) of images (including motion) to store without redundancy currently.
Please, provide me the links for sites where you and them will warranty me what my 3TB+ content isn't going to be trashed and gone after ten years, at least (the life time of any RAID).

Ten years is about $50 per year for at least 3 TB currently and multiple as you promise, in terms of the price for RAID 5 of 3 TBs.

I'm eagerly waiting for your response, Dante.

Yours, Ko.
 
I guess my method is unsophisticated but simple... I have all active files on the Mac's internal 3Tb Fusion drive automatically backed up hourly with Time Machine to an external drive via USB3. I use CCC to make a clone every few days to another external via Firewire 800 (I keep this drive in a fireproof safe). I figured since these are both backups, Thunderbolt was unnecessary and added $100 or so to the drive cost. Moderate speed seems entirely satisfactory. If I were actively using datafiles or applications from an external that would be a different story.
 
Raid is not a substitute for backup, it is only a first level protection against catastrophes.

You are right that raid is vulnerable when a disk is down and that rebuild times are long. But that is where your backup if for. When a disk is down, you make sure your backup is up to date (and raid gives you that important time!), replace the set as other disks will follow if they are all of the same brand/type/date, and repopulate your new array with the backup. Might be a good idea to keep the set for a time to make sure you have everything important off it.

And this doesn't protect you against a raid controller failure.

I use a system similar to yours (but I don't have 5TB), main data on a hardware raid 5 in the pc, a local "backup" on a single HD in the pc (not mounted so no accidental writes to it) and external backups that get sync'ed from time to time and stored at my parents.
 
RAID 5 was relevant when drive space was expensive - the downsides are low speed and hardware dependency. In my experience, you'll find that suitable spare drives have long gone the way of the dodo by the time your first drive fails (so that you have to resort to well-worn used drives from ebay or spares sold at extortionate prices through the official service channels of industry-strength server makers) - and the controller (or anything compatible to your drive layout) won't fit your next computer either. These days, RAID 1 is the way to go - both faster and easier to maintain, and much less vulnerable to drive size/type mismatches (usually anything at least as big and fast will do as a substitute whenever a drive fails).
 
I backup daily with TimeMachine on an external HD, of which I have two which are exchanged every week and the one not used for this week back up is in a different location.
More I copy and update (by exporting it) the images folder (included the LR catalog and associated files) on another portable HD which can eventually used with a laptop when traveling etc, again two different exchanged once a month.
So total I have 4 copies on different HDs of my photo files. It only needs a little discipline...
robert
 
I back up image files on one external HD, with the goal to buy in January two addition HD's for this purpose. I have two or three external HD's at work for data back-up. Sensitive data sets are saved on a computer that is locked up in some room which is IT secured at all times. Better be safe than be sorry one day,
 
Agree with photomoof.
I have to use combination of both.
My most valuable pictures (not so many) are uploaded to Google.
Which isn't cheap solution for large volume.
I'll try to upload my most valuable video to Flickr, for storage, since it is unlimited at reasonable price.
But I"m not aware, personally, of any other on-line storages with known names and large storage capacities for reasonable price.
My another alternative for redundancy is to duplicate my current 3TB of media to another single drive and store it not at home.
 
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