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Drobo S vs. Promise DS 4600 vs. other?

post #1 of 13
Thread Starter 
Hey guys,

I'm currently trying to choose between the Drobo S and the Promise DS4600. The DS4600 is way cheaper so that's an advantage

Anyway, the raid's purpose for me would be to serve as my main storage for photography, which means I need it to be very fast so I can access my photos with no hiccups.

I am a Mac user and I thought about connecting it using Firewire 800.

Do you think the Promise would be fast enough for this purpose? What about the Drobo S? Which is better?
post #2 of 13
How many drives are you planning on using and what kind of RAID setup are you going to use?

Firewire 800 is going to be quite a bit faster than USB 2.0 but not as fast as eSATA if that's an option on your computer. There are Expresscard eSATA adapters if your computer has a slot for them (Macbook Pro? What kind of computer do you have?).

I doubt one is going to be significantly faster than the other. It'll mainly depend on what drives you use and how you set them up in a RAID array.

One concern I'd have with it since it sounds like this is important data is reliability of the controllers. Read a LOT of reviews on each before you decide anything.
post #3 of 13
Thread Starter 
Hey,
I was planning to purchase 2 drives so that one would mirror the other (if you think I should better buy more - let me know). Regarding RAID setup - haven't decided yet. I understand 5 is good.

I have a 24" iMac (previous gen) and I don't have an eSATA slot.

Do you know if these drives should be fast enough for my needs? Is it a good idea to use them as the main storage for my photo library?

Most reviews regarding both drives are positive, although I've read some complaints regarding failed controllers in both cases.

Quote:
Originally Posted by smax View Post

How many drives are you planning on using and what kind of RAID setup are you going to use?

Firewire 800 is going to be quite a bit faster than USB 2.0 but not as fast as eSATA if that's an option on your computer. There are Expresscard eSATA adapters if your computer has a slot for them (Macbook Pro? What kind of computer do you have?).

I doubt one is going to be significantly faster than the other. It'll mainly depend on what drives you use and how you set them up in a RAID array.

One concern I'd have with it since it sounds like this is important data is reliability of the controllers. Read a LOT of reviews on each before you decide anything.
post #4 of 13
Wait, two drives to go into one enclosure, or 2 separate enclosures to mirror each other (or to just have one as a backup?)? Sorry, your wording's a bit vague.
post #5 of 13
Thread Starter 
Quote:
Originally Posted by smax View Post

Wait, two drives to go into one enclosure, or 2 separate enclosures to mirror each other (or to just have one as a backup?)? Sorry, your wording's a bit vague.

Just one enclosure. I planned to put 2 drives into it, but if it's problematic I can also put 3 or 4...
post #6 of 13
One final question: How much space do you want on this volume anyway?
post #7 of 13
OK, I gotta get to bed, but I'll post this for you to chew on and for other people to correct me on.

OK, here's the quick rundown on RAID from someone who's never dealt with it personally and doesn't know everything there is to know about it.

RAID is NOT a backup solution. If you delete a file from a RAID volume, it's gone on all of the disks involved in that volume. There's no protection against accidentally deleting or modifying a file at all (which I think would be a good thing considering what you're using these drives for). If you're thinking RAID is used as a backup solution, stop right here.

RAID 0 aside, it's effectively a way to prevent data loss from a hardware failure (i.e. one disk dies). You mention wanting RAID 5 with 2 drives, but RAID 5 requires at least 3 drives. The best you could do with 2 drives is RAID 1, which wouldn't give you any performance benefit at all as the two drives just mirror each other. For the best read/write speed benefit while maintaining a 1-disk fault tolerance, the best you could do it pack as many drives as you can into the enclosure and set up a RAID 5 array.

This brings up another issue though: How fast will the actual maximum read/write speeds be? This is important because even if your RAID array can somehow read at 200 MB/s, you have an interface that can only handle 800Mb/s (100MB/s) on a good day. This is assuming a best-case scenario in terms of speed and assuming the chips in the enclosures are VERY good. Basically, you can throw as much money as you want at the problem and cram as many disks in there as you can, but at some point it's going to make no difference at all. Where is that point? I have no clue.

If it were up to me, I'd set up the enclosure with a fault tolerant RAID array (RAID 1 or 5, depending on how fast I wanted it to be and how much space I needed in the volume) for everyday use. That way if one drive takes a shit one day, you can just replace the dead drive with an identical one, rebuild your volume, and be on your merry way (hopefully).

To account for actually backing up the data on that array, I'd also have another completely separate drive (a single 2TB/3TB drive or another array if you wanted to be super paranoid about disk failures or if you needed more space) set to do scheduled incremental backups at whatever interval you want. Speed shouldn't be your primary concern here as you shouldn't even think of working using your backup drives (unless you're constantly changing several GB worth of data between backups and the actual duration of the backup process becomes an issue), so worry more about fault tolerance than speed benefits. Depending on how paranoid you are, this can get awfully expensive. It all boils down do exactly how important that data is and how much you really want to invest to protect it.

Of course, I have no clue if this is for professional purposes or not. I trust you can figure out for yourself exactly how valuable your data is and to what (possibly insane) lengths you'll go to protect it.


EDIT: Take a look at the Wikipedia article for a bit of light reading on the subject if you want. http://en.wikipedia.org/wiki/RAID

Actually, glancing over the article again, it would appear that Mac OSX doesn't support software RAID 5 so (Please, anyone correct me if I'm wrong!!) I think you'll need to ensure that the enclosure you get supports it at the hardware level. I guess you could try a RAID 1+0 array which would require 4 drives for any benefit if you have to use software RAID.
post #8 of 13
Thread Starter 
Quote:
Originally Posted by smax View Post

OK, I gotta get to bed, but I'll post this for you to chew on and for other people to correct me on.

OK, here's the quick rundown on RAID from someone who's never dealt with it personally and doesn't know everything there is to know about it.

RAID is NOT a backup solution. If you delete a file from a RAID volume, it's gone on all of the disks involved in that volume. There's no protection against accidentally deleting or modifying a file at all (which I think would be a good thing considering what you're using these drives for). If you're thinking RAID is used as a backup solution, stop right here.

RAID 0 aside, it's effectively a way to prevent data loss from a hardware failure (i.e. one disk dies). You mention wanting RAID 5 with 2 drives, but RAID 5 requires at least 3 drives. The best you could do with 2 drives is RAID 1, which wouldn't give you any performance benefit at all as the two drives just mirror each other. For the best read/write speed benefit while maintaining a 1-disk fault tolerance, the best you could do it pack as many drives as you can into the enclosure and set up a RAID 5 array.

This brings up another issue though: How fast will the actual maximum read/write speeds be? This is important because even if your RAID array can somehow read at 200 MB/s, you have an interface that can only handle 800Mb/s (100MB/s) on a good day. This is assuming a best-case scenario in terms of speed and assuming the chips in the enclosures are VERY good. Basically, you can throw as much money as you want at the problem and cram as many disks in there as you can, but at some point it's going to make no difference at all. Where is that point? I have no clue.

If it were up to me, I'd set up the enclosure with a fault tolerant RAID array (RAID 1 or 5, depending on how fast I wanted it to be and how much space I needed in the volume) for everyday use. That way if one drive takes a shit one day, you can just replace the dead drive with an identical one, rebuild your volume, and be on your merry way (hopefully).

To account for actually backing up the data on that array, I'd also have another completely separate drive (a single 2TB/3TB drive or another array if you wanted to be super paranoid about disk failures or if you needed more space) set to do scheduled incremental backups at whatever interval you want. Speed shouldn't be your primary concern here as you shouldn't even think of working using your backup drives (unless you're constantly changing several GB worth of data between backups and the actual duration of the backup process becomes an issue), so worry more about fault tolerance than speed benefits. Depending on how paranoid you are, this can get awfully expensive. It all boils down do exactly how important that data is and how much you really want to invest to protect it.

Of course, I have no clue if this is for professional purposes or not. I trust you can figure out for yourself exactly how valuable your data is and to what (possibly insane) lengths you'll go to protect it.


EDIT: Take a look at the Wikipedia article for a bit of light reading on the subject if you want. http://en.wikipedia.org/wiki/RAID

Actually, glancing over the article again, it would appear that Mac OSX doesn't support software RAID 5 so (Please, anyone correct me if I'm wrong!!) I think you'll need to ensure that the enclosure you get supports it at the hardware level. I guess you could try a RAID 1+0 array which would require 4 drives for any benefit if you have to use software RAID.

I understand that RAID is not a complete backup solution. I plan to supplement it with an online backup.

Regarding my needs:

I want to use the RAID as the main storage of my photo library. I would probably put some more stuff inside and would also want it to backup my Mac with Time Machine. All in all - I don't need more than 1 TB of storage for at least the upcoming year or two. Maybe 2TB if I want to absolutely be on the safe side. Besides the need for the storage, I need it to be redundant and reliable (I am also backing up to an online service) and not less important - the data access should be FAST as the RAID would be used as the main storage for my photos.

I guess I will buy several 1-2 TB drives (2-3 for the Drobo S, maybe 4 for the other drives since they are cheaper) and I really don't see a need for me to have more than 5 TB total storage on the RAID (including redundancy). I do want to be able to easily replace a faulty drive with a different one if and when a drive crashes. It seems it would also be important that the device would be able to accept a different kind of drive (not the same as the other, currently installed drives) as one cannot tell if a specific drive model would be available in a year or two from the date of purchase.

Any recommendations/observations?

Thanks again.
post #9 of 13
If you only need 2TB get a 2 bay RAID 1 enclosure and drop a couple 2 TB drives in them.

This one seems reasonable:

http://eshop.macsales.com/item/Newer...gy/GM8QKIT0GB/

I'd drop a couple of these in there and call it a day:

http://www.newegg.com/Product/Produc...82E16822136514

$130 + $200 for 2 TB RAID 1 for about the same price as the bare Promise enclosure.

Building out an uber array to "future proof" it seems counter productive if the past is a guide. A couple, three years ago it took a 4 bay enclosure with uber 500GB drives to get a 2GB array. If you went the drobo route it was around $900+. Now it's a cheap single drive.

You can spend the $ on a Dorbo S but if your near term needs are only 1TB that's overkill. Say it takes you 2 years to fill that 2TB array. Figuring the 4TB drives show in 2011 and the 5TBs in 2012 you can probably get the 4TB drives for $99 in 2012.

Maybe by then the macs will be running lightpeak. The 2008 dorbo owners are missing eSATA...
post #10 of 13
Thread Starter 
Hey there,
I've been giving the whole thing some more thought (and been consulting some guys) and I got to the conclusion that I was probably going in the wrong path.
It seems that a better solution is upgrading the internal HD of my Mac (I've seen that it's possible to upgrade it to 1-2 TB - I'm going for 1.5 TB) and to use an external drive as a Time Machine backup (plus an online backup, for off-site - as I already do now).
Do you agree with this assessment? It seems it will give me better security, since the data is backed up into two actually different places (+offsite) with no single-point-of-failure (the RAID's controller). Plus - it will give me the best speeds to access my data - and it will be cheaper.
Anyway, under this scenario I don't really need the external drive to be that secured/redundant or even fast. However, it seems I would still be better off with a RAID as it is more expendable, can offer more storage and cheaper than a regular external drive (I will soon be getting rid of 2 drives of 1TB each that I have nothing to do with, now when my storage needs grew). I was thinking about buying this enclosure: http://eshop.macsales.com/item/Other...g/MEPT934AL2C/
dropping 2X2TB drives inside it and configuring it to RAID 0 (I don't need the redundancy - just the extra storage).
What do you think?
Thanks and I wish you all a merry Christmas
post #11 of 13
I'd say upgrading the internal drive's probably your best bet. There are even 3GB drives on the market now, so take a look at those too. An external for Time Machine is a good idea too, the bigger the better.

In general, RAID 0 is a bad idea. Not needing redundancy is one thing, but purposefully making your external drive MORE prone to failure is pretty stupid in my book.
post #12 of 13
Thread Starter 
Quote:
Originally Posted by smax View Post

In general, RAID 0 is a bad idea. Not needing redundancy is one thing, but purposefully making your external drive MORE prone to failure is pretty stupid in my book.

Any other suggestions for an expendable storage of at least 4 GB on the cheap? I was planning on buying that OWC enclosure that I linked to with two drives of 2TB (and RAID 0).

Drobo is way too expensive for me. I don't need it either...
post #13 of 13
Quote:
Originally Posted by lirand View Post

Any other suggestions for an expendable storage of at least 4 GB on the cheap? I was planning on buying that OWC enclosure that I linked to with two drives of 2TB (and RAID 0).

I dunno why they gimped that enclosure to not provide RAID 1 but I would shell out the extra $15 for eSATA and RAID 1 capability. The Oxford 934DSb is typically used in single drive enclosures.

Or at least go with the $109 version with the Oxford 936DS and RAID 1 and eSATA.

http://eshop.macsales.com/item/Other...ng/MEFW936AL2/

Dunno why they recommend the Maximus over that enclosure as they both have the same chipset. I guess it must be better because it's painted black or something but you can save $20. Actually, I kid. The Maximus case does look better designed and it has external indicator lights to tell you if a drive went kaput. Kinda useful to be able to see at a glance...and I think it comes bundled with some software you may or may not want.
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