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ew1
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Help needed understanding RAID (Glotrends 25-R)

Sat Jan 04, 2020 6:27 am

Hi

Forgive me if this is not the appropriate place to be asking about this.


    I have a RAID enclosure. It’s the Glotrends 25-R 2.5” Dual Bay SATA enclosure (DON’T buy it. It’s not a great product and there appears to be no customer support for it any longer).

    Inside it I have two 2TB SATA drives.

    I’m using it in RAID 1 mode and the company describe it as a "hardware RAID solution” which I think means that you don’t have to do any work inside your computer to set up the RAID functionality. It’s all done inside the product itself.

    I have already followed the setup instructions but that was a few months ago so I can’t remember exactly what they were. But I think it was something as simple as opening Disk Utility and formatting the drive.


I have a couple of questions.


The first few questions are about understanding how RAID is represented in Disk Utility.


1. I have two 2TB drives in the RAID enclosure. When I view it in Disk Utility, Disk Utility only sees one 2TB drive (see attached image). Why is this? Is it because the RAID enclosure presents the two drives as one?


Screenshot 2020-01-04 at 14.15.08.png
Screenshot 2020-01-04 at 14.15.08.png (737.05 KiB) Viewed 235 times








2. If this is correct, isn't the device then fully ready for RAID 1 use without needing to partition it?

3. The reason I ask that last question is that the setup instructions said that you must partition the device. If this particular RAID enclosure presents the two drives as one, is it actually necessary for me to partition the device in order to use it in RAID 1 mode? If I partition the drive, I end up with two 1TB drives in Disk Utility (as if there is only one 2TB drive in the enclosure) and this seems pointless to me.



The next questions are specific to this product and should really be answered by customer service but like I said, there’s no hope of that now.

4. I’ve set the product to RAID 1 mode using the switch that is on the outside of the enclosure but how do I know for sure that this device is actually operating RAID 1 successfully? Disk Utility doesn’t show the two drives in the device. It just shows one so how do I know that this product is definitely doing what it’s supposed to?

5. Also, how am I supposed to know if one of the drives fails and needs to be replaced? I assumed that with RAID there would be some interface that allows you to view both drives inside the enclosure and view the status/condition of each drive so that you would know when one needs to be replaced. But there doesn’t seem to be a way to see this. Disk Utility only sees one 2TB drive and the product didn’t come with any software that allows you to view the contents of the enclosure.


Any ideas?

Thanks
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Ploki
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Re: Help needed understanding RAID (Glotrends 25-R)

Sat Jan 04, 2020 9:54 am

1) RAID 1 is mirroring.
That means both drives work as one, so if you lose one drive the other is an exact clone of it.
It does not offer any performance benefits.

RAID 0 is striping.
This means two drives will act as one, data being split between the two.
The result is 2x faster speed minus overhead.
if one drive fails, the whole array fails and second drive is also unreadable.

2) yes, you can use it as it is if you want redundancy.
that way when one drive fails you simply replace it and it will copy s#!+ over to have a mirror again.

3) RAID has nothing to do with partitioning.
Your disk is already partitioned anyway. A single partition is still a "partitioned" drive.

4) if it has two 2TB drives and you only see 2TB it's probably in RAID 1.
It could also be in JBOD with one drive failed, but unlikely i guess.

5) There should be some indications on the enclosure if a drive fails. If it's a hardware RAID it generally doesn't need to communicate with the OS, so you won't see this in disk utility.

I have an old CineRaid 2x2.5" portable RAID, and i knew that one disk failed because it stopped working, but I had it in RAID 0. (I still do)

i'll replace it with a single 2TB USB3.1 gen2 SSD instead... sick of spinners :)
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angelonyc
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Re: Help needed understanding RAID (Glotrends 25-R)

Tue Jan 14, 2020 5:42 am

If you buy a multi disk RAID you get excellent speed improvements. I have two Thunderbay RAID set-ups from OWC. These are 4 bay drives. I use, and they recommend RAID 5. This gives you significant speed response. and should one of the drives fail, you can completely recover the data. I have a huge Kontakt library, and UVI library on it. It has never bogged down. The system comes with SOFTRAID, now a part of OWC. This software will let you choose which flavor of RAID you want mirroring, or 4 single drives. After 5 years I have had one disk fail. SOFTRAID monitors the drive, and will tell you well in advance, that failures are starting to happen.

You can buy a 4 bay Thunderbolt 2 speed RAID, or a 5 bay Thunderbolt 3 speed. The Thunderbolt 3 speed will also run at the slower Thunderbolt 2 speed. I use a lot of tracks, The system has never failed me in playing back libraries. For me the extra speed and expense of Thunderbolt 3 is not necessary, for doing audio. Extensive video work, would probably be better. Far cheaper than SSD's, plus with the RAID 5, you have the benefit of recovering any data that becomes corrupt.

Recovering the data from a corrupt drive is a lengthy process. I have a 24 terabyte RAID. When one of the Drives died, I replaced it with a new drive, took about 10 hours for SOFTRAID to recover and and reconstitute the new drive. The RAID system will even send you an email, before failure.
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ew1
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Re: Help needed understanding RAID (Glotrends 25-R)

Mon Jan 20, 2020 12:56 pm

Ploki wrote:
1) RAID 1 is mirroring.
That means both drives work as one, so if you lose one drive the other is an exact clone of it.
It does not offer any performance benefits.

RAID 0 is striping.
This means two drives will act as one, data being split between the two.
The result is 2x faster speed minus overhead.
if one drive fails, the whole array fails and second drive is also unreadable.

2) yes, you can use it as it is if you want redundancy.
that way when one drive fails you simply replace it and it will copy s#!+ over to have a mirror again.

3) RAID has nothing to do with partitioning.
Your disk is already partitioned anyway. A single partition is still a "partitioned" drive.

4) if it has two 2TB drives and you only see 2TB it's probably in RAID 1.
It could also be in JBOD with one drive failed, but unlikely i guess.

5) There should be some indications on the enclosure if a drive fails. If it's a hardware RAID it generally doesn't need to communicate with the OS, so you won't see this in disk utility.

I have an old CineRaid 2x2.5" portable RAID, and i knew that one disk failed because it stopped working, but I had it in RAID 0. (I still do)

i'll replace it with a single 2TB USB3.1 gen2 SSD instead... sick of spinners :)


Thanks for that.

All I can see on the outside of the enclosure are are these two holes labelled HDD1 and HDD2. Maybe they have lights in them that will switch on when there is an error with a drive. What do you think?


DSC_0805.JPG
DSC_0805.JPG (6.17 MiB) Viewed 144 times
• Logic Pro 9.1.8
• OS X 10.10.5
• 2013 iMac
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ew1
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Joined: Mon Aug 24, 2015 4:32 pm

Re: Help needed understanding RAID (Glotrends 25-R)

Mon Jan 20, 2020 12:59 pm

angelonyc wrote:
If you buy a multi disk RAID you get excellent speed improvements. I have two Thunderbay RAID set-ups from OWC. These are 4 bay drives. I use, and they recommend RAID 5. This gives you significant speed response. and should one of the drives fail, you can completely recover the data. I have a huge Kontakt library, and UVI library on it. It has never bogged down. The system comes with SOFTRAID, now a part of OWC. This software will let you choose which flavor of RAID you want mirroring, or 4 single drives. After 5 years I have had one disk fail. SOFTRAID monitors the drive, and will tell you well in advance, that failures are starting to happen.

You can buy a 4 bay Thunderbolt 2 speed RAID, or a 5 bay Thunderbolt 3 speed. The Thunderbolt 3 speed will also run at the slower Thunderbolt 2 speed. I use a lot of tracks, The system has never failed me in playing back libraries. For me the extra speed and expense of Thunderbolt 3 is not necessary, for doing audio. Extensive video work, would probably be better. Far cheaper than SSD's, plus with the RAID 5, you have the benefit of recovering any data that becomes corrupt.

Recovering the data from a corrupt drive is a lengthy process. I have a 24 terabyte RAID. When one of the Drives died, I replaced it with a new drive, took about 10 hours for SOFTRAID to recover and and reconstitute the new drive. The RAID system will even send you an email, before failure.



Thanks. For the purposes of backups/redundancy, do you think this way is better than using Carbon Copy Cloner?
• Logic Pro 9.1.8
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Ploki
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Re: Help needed understanding RAID (Glotrends 25-R)

Mon Jan 20, 2020 1:47 pm

They might. No manual eh?
Probably it communicates everything from those two. I.e., "lights on" = everything ok, "flashing lights" = problem

RAID 1 is better than using carbon copy cloner because its instantaneous, but you have both drives in a single enclosure which means that if you lose it or if it gets heavy damage both drives get hit.

With CCC you'll likely have two separate drives, and two copies.

Hardware failure of the actual drive is only one way to destroy or lose data. :)
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ew1
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Re: Help needed understanding RAID (Glotrends 25-R)

Mon Jan 20, 2020 2:08 pm

Ploki wrote:
They might. No manual eh?
Probably it communicates everything from those two. I.e., "lights on" = everything ok, "flashing lights" = problem

RAID 1 is better than using carbon copy cloner because its instantaneous, but you have both drives in a single enclosure which means that if you lose it or if it gets heavy damage both drives get hit.

With CCC you'll likely have two separate drives, and two copies.

Hardware failure of the actual drive is only one way to destroy or lose data. :)



Thanks. I still don't understand why my Disk Utility shows only one 2TB drive though. I would expect that in RAID 1, you would see the 2 drives in disk utility. Is it totally normal for disk utility to just show one drive in this situation?
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angelonyc
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Re: Help needed understanding RAID (Glotrends 25-R)

Mon Jan 20, 2020 3:40 pm

If there is an LED, it will usually blink when there is activity, reading or writing. I can't quite follow your situation, which RAID you are using. It would depend on the RAID set-up is Mac OS creating the RAID, or does the RAID itself, have the software in it. My Thunderbolt 4 bay (RAID 5) shows up as one drive. The RAID system uses Softraid (software) It shows me the 4 drives, and will give a report, should one of the drives acts up..

In about Mac info. The OS sees the RAID as one drive. If you bought this Drive RAID system, you should check your manual, or contact manufacture. I would assume a disk utility might see the RAID as one drive, seeing as Mac OS sees it as one drive. I just opened 'Disk Genius', it sees my RAID system as one drive, not the 4 drives.

In my 'Softraid' software (program that creates, monitors the RAID system). It sees the four drives, and will tell me which of any drive is malfunctioning. If one drive is corrupted. You hit a command or two, remove bad drive, put in new one, hit another function and it 'recovers' data from the other three drives to make a complete working system. The rebuilding takes quite a long time. Something like 8 or more hours for a 6TB drive.
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Ploki
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Re: Help needed understanding RAID (Glotrends 25-R)

Tue Jan 21, 2020 12:16 pm

ew1 wrote:
Thanks. I still don't understand why my Disk Utility shows only one 2TB drive though. I would expect that in RAID 1, you would see the 2 drives in disk utility. Is it totally normal for disk utility to just show one drive in this situation?


Because it's a hardware raid, all the "mirroring" is done on the enclosure so disk utility only sees a single physical drive.

If you'd set the enclosure in JBOD and make a software raid (via disk utility) it would show you 2 drives because in that case, the OS would manage mirroring.
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ew1
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Re: Help needed understanding RAID (Glotrends 25-R)

Fri Feb 14, 2020 9:56 am

Ploki wrote:
They might. No manual eh?
Probably it communicates everything from those two. I.e., "lights on" = everything ok, "flashing lights" = problem

RAID 1 is better than using carbon copy cloner because its instantaneous, but you have both drives in a single enclosure which means that if you lose it or if it gets heavy damage both drives get hit.

With CCC you'll likely have two separate drives, and two copies.

Hardware failure of the actual drive is only one way to destroy or lose data. :)


Thanks. But with RAID, you only get file backup/storage and not an actual bootable drive right? And you do get a bootable drive with CCC, right?
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Ploki
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Re: Help needed understanding RAID (Glotrends 25-R)

Fri Feb 14, 2020 10:48 am

RAID 1 is a literal block-by-block clone, it should be bootable if i recall correctly
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