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Thoughts on Areca RAID...
- Thread starter SnapperUK
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This seems to be an interesting read.
http://www.larryjordan.biz/product-review-areca-8050-thunderbolt-raid/
Yes, I used one for a movie I produced in Atlanta last year,
we had a two station Media Composer set up off of the raid.
no problems,
However, we used MaxxDigital's version of the Areca
http://www.maxxdigital.com/thunderraid-380.html
zero problems, Editor said it was the fastest responding avid system have ever used.
That Larry Jordan article was amusing. He didn't set it up right at all, and it took until December 17th for someone to post a comment that he screwed up the setup.
I was suspicious that the review might be poor when he said he had never heard of Areca, and that suspicion was confirmed as I kept reading. If one doesn't know what they're doing, they might want to learn about a subject before writing a whole review on it. At least he eludes to the fact that he is walking in blindly when he mentions, "...new users don't know anything..."
When I bought my Areca gear, I had done a lot of research beforehand, and learned more still as I set up the gear, but you won't see me complaining about the fact that English is not the company's primary language. Areca is very good at answering questions, and they know the answers better than anyone, because the guys you talk to on the phone/email are the same ones that built the gear! I understood their English just fine, personally.
I was suspicious that the review might be poor when he said he had never heard of Areca, and that suspicion was confirmed as I kept reading. If one doesn't know what they're doing, they might want to learn about a subject before writing a whole review on it. At least he eludes to the fact that he is walking in blindly when he mentions, "...new users don't know anything..."
When I bought my Areca gear, I had done a lot of research beforehand, and learned more still as I set up the gear, but you won't see me complaining about the fact that English is not the company's primary language. Areca is very good at answering questions, and they know the answers better than anyone, because the guys you talk to on the phone/email are the same ones that built the gear! I understood their English just fine, personally.
I built out an Areca 8050 box for my edit bay and have had a great experience with it so far. At the time it was the only option for a bring-your-own-drive Thunderbolt solution, as I didn't want to buy a pre-filled Pegasus if I could avoid it. I filled it with 8 (relatively inexpensive) 3TB Western Digital Barracuda drives. It's configured for RAID 6, so I can have survive two drive failures while still having 18TB usable space for all my footage.
I will warn that I originally had the RAID hooked up to my 2011 17" MBP, and soon realized that the Thunderbolt bus on that machine couldn't handle 2 Thunderbolt displays AND the Areca without drastically reducing the R/W speeds on the Areca (as well as incurring various other performance hits to the performance of the machine). I'm now renting a 2013 iMac which has a newer Thunderbolt chipset (as well as 2 ports) as a stop gap until my Mac Pro arrives. I'm happy to report that the Areca is performing wonderfully on the new system under my normal Avid/After Effects stress. I don't believe I've run Blackmagic's disk speed test since I received the iMac, but I can try to remember to do that when I get home from work if you'd like?
Here's a thread I'd written about my peculiar findings using the Areca on that 2011 MBP. https://discussions.apple.com/thread/5263753
It's worth noting that most of my findings probably aren't directly due to the Areca itself, but simply because I was maxing out the bandwidth of the Thunderbolt channel.
I will warn that I originally had the RAID hooked up to my 2011 17" MBP, and soon realized that the Thunderbolt bus on that machine couldn't handle 2 Thunderbolt displays AND the Areca without drastically reducing the R/W speeds on the Areca (as well as incurring various other performance hits to the performance of the machine). I'm now renting a 2013 iMac which has a newer Thunderbolt chipset (as well as 2 ports) as a stop gap until my Mac Pro arrives. I'm happy to report that the Areca is performing wonderfully on the new system under my normal Avid/After Effects stress. I don't believe I've run Blackmagic's disk speed test since I received the iMac, but I can try to remember to do that when I get home from work if you'd like?
Here's a thread I'd written about my peculiar findings using the Areca on that 2011 MBP. https://discussions.apple.com/thread/5263753
It's worth noting that most of my findings probably aren't directly due to the Areca itself, but simply because I was maxing out the bandwidth of the Thunderbolt channel.
Many thanks for sharing your experiences.
Having 3 Thunderbolt buses on the nMP should be a tremendous improvement.
When I get my nMP in March, I will use Bus 0 for displays, and Bus 1 and 2 for I/O.
It will be very interesting to see what kind of performance improvements you will realize on your nMP.
Great. Thanks for your experiences. Looks like this is the way forward for me.
Found a great deal on it but didn't want to take the plunge until I had heard from a few users.
Slightly put off by the look of the thing. It is ugly.
Heard from a UK dealer that the Thunderbolt 2 version may be out at the end of March. But given that I'll only be putting HDDs in there then I wouldn't see any speed benefit.... Right?
Found a great deal on it but didn't want to take the plunge until I had heard from a few users.
Slightly put off by the look of the thing. It is ugly.
Heard from a UK dealer that the Thunderbolt 2 version may be out at the end of March. But given that I'll only be putting HDDs in there then I wouldn't see any speed benefit.... Right?
I don't believe I'm maxing out the TB1 channel when the thing's filled with 7200rpm drives, so I'd say it's probably safe to assume that waiting for TB2 could be overkill... but I don't know that for certain.
It's definitely not the prettiest device I've ever bought, but once I tucked it away into a separate piece of (well ventilated) furniture I don't have to look at the thing any more! Of note, it does have many very bright LEDs up front, so if you do place it somewhere visible you're gonna get a bit of a light show when you start pinging it for data.
It's definitely not the prettiest device I've ever bought, but once I tucked it away into a separate piece of (well ventilated) furniture I don't have to look at the thing any more! Of note, it does have many very bright LEDs up front, so if you do place it somewhere visible you're gonna get a bit of a light show when you start pinging it for data.
Works Flawlessly - Quiet except for Startup/Shutdown
I have Areca 8050 Running on nMP 6core along with a Pegasus R4 for just over 1 week. For the Areca:
I loaded all drive bays with identical Toshiba 3TB 7200 drives Raid 5. 21TB.
Makes a bit of noise from all of those drives, but watch out for sleep mode. I believe there is a problem with sleep on nMP in general but the Areca seems to handle it OK, but the fans all come on during a power change, sounds like a wind tunnel at Power ON/OFF or Sleep / Wake.
Other than that there are no problems. For configuration there were a lot of options that I left as the default since I didn't know how to optimize them. If anyone has an further input I would be interested.
I run a photo editing and printing business and this drive seems a bit bigger than what I need today, but I am hoping it lasts a while and lets me grow into it. I wanted all of the same drives so I just filled the thing up.
My only minor quibble with the Areca is the 3 lights in the centre of the unit pulse on /off about every 3 seconds. Just a bit distracting.
Don't forget to get a UPS to power all of those drives.
Speed: 691 Read, 613 write with bursts over 700 MB/S - seems to vary a lot.
The Pegasus R4 (old TB1) has serious sleep wake issues on nMP but works fine on MBP 17". Have a trouble call into Apple on that.
I documented my experience configuring it: http://jeffgardner.ca/Blog/?p=718
One point - I had serous problems trying to update the firmware using Safari 7. There would be no response - so I switched to Firefox and had no problems after that. Couldn't load the BIOS file at all with Safari.
If I were doing it over again, I would update the firmware before installing the drives and performing Raid Initialization. Mine came with the previous firmware (just one version back from current) but it had weird hangs on the Raid Initialization.
I bought mine from OWC - and they had a good deal on the drives. It did not come with a TB cable which I thought it would but by the time I placed my order that offer had expired.
I have Areca 8050 Running on nMP 6core along with a Pegasus R4 for just over 1 week. For the Areca:
I loaded all drive bays with identical Toshiba 3TB 7200 drives Raid 5. 21TB.
Makes a bit of noise from all of those drives, but watch out for sleep mode. I believe there is a problem with sleep on nMP in general but the Areca seems to handle it OK, but the fans all come on during a power change, sounds like a wind tunnel at Power ON/OFF or Sleep / Wake.
Other than that there are no problems. For configuration there were a lot of options that I left as the default since I didn't know how to optimize them. If anyone has an further input I would be interested.
I run a photo editing and printing business and this drive seems a bit bigger than what I need today, but I am hoping it lasts a while and lets me grow into it. I wanted all of the same drives so I just filled the thing up.
My only minor quibble with the Areca is the 3 lights in the centre of the unit pulse on /off about every 3 seconds. Just a bit distracting.
Don't forget to get a UPS to power all of those drives.
Speed: 691 Read, 613 write with bursts over 700 MB/S - seems to vary a lot.
The Pegasus R4 (old TB1) has serious sleep wake issues on nMP but works fine on MBP 17". Have a trouble call into Apple on that.
I documented my experience configuring it: http://jeffgardner.ca/Blog/?p=718
One point - I had serous problems trying to update the firmware using Safari 7. There would be no response - so I switched to Firefox and had no problems after that. Couldn't load the BIOS file at all with Safari.
If I were doing it over again, I would update the firmware before installing the drives and performing Raid Initialization. Mine came with the previous firmware (just one version back from current) but it had weird hangs on the Raid Initialization.
I bought mine from OWC - and they had a good deal on the drives. It did not come with a TB cable which I thought it would but by the time I placed my order that offer had expired.
Areca 8050 - Thunderbolt Sleep Wake Issues Mac Pro 2013 (6,1)
When the Mac Pro goes to sleep, so does my Areca 8050 Raid 5 - 21TB Drive for about 1-2 seconds. After about 1 second, the Areca and the Mac Pro wake up. If the Areca is not connected, the Mac Pro to sleep normally. In other words, the Areca is the cause of the wake 1 second after sleep.
Problem does not happen on Pegasus R4 drive.
I will be posting any solutions to this if/when I get them on this posting:
https://forums.macrumors.com/threads/1702539/
When the Mac Pro goes to sleep, so does my Areca 8050 Raid 5 - 21TB Drive for about 1-2 seconds. After about 1 second, the Areca and the Mac Pro wake up. If the Areca is not connected, the Mac Pro to sleep normally. In other words, the Areca is the cause of the wake 1 second after sleep.
Problem does not happen on Pegasus R4 drive.
I will be posting any solutions to this if/when I get them on this posting:
https://forums.macrumors.com/threads/1702539/
ARECA Thunderbolt 2 vs. Pegagus on cost performance
I was about to order an empty Pegasus2-R4 but decided to google if there are any alternatives out there with TB2 I found the ARECA...
My questions are simple.
1. Who sells the ARECA online and ships to Canada?
2. Can I buy teh ARECA empty and populate with my own HDD?
3. Seems the performance of AREACA is better that Peg2... (http://forums.creativecow.net/thread/197/859967)
Seems everytime I post something then keep searching while I wait for someone to post I find the answers I am looking for...
For price performance that suits me looks like I will take the PEg2 R4 empty from apple and populate it myself.
I was about to order an empty Pegasus2-R4 but decided to google if there are any alternatives out there with TB2 I found the ARECA...
My questions are simple.
1. Who sells the ARECA online and ships to Canada?
2. Can I buy teh ARECA empty and populate with my own HDD?
3. Seems the performance of AREACA is better that Peg2... (http://forums.creativecow.net/thread/197/859967)
Seems everytime I post something then keep searching while I wait for someone to post I find the answers I am looking for...
For price performance that suits me looks like I will take the PEg2 R4 empty from apple and populate it myself.
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I bought mine from OWC. They supply it empty but offer a great discount on drives if you want that.
http://eshop.macsales.com/item/Areca/ARC8050/
The current version is TB1, I am not sure that TB2 with 8 drives maxes out 10mbps.
If you have the new mac pro you should be aware of sleep issues, I still get that with this drive.
http://eshop.macsales.com/item/Areca/ARC8050/
The current version is TB1, I am not sure that TB2 with 8 drives maxes out 10mbps.
If you have the new mac pro you should be aware of sleep issues, I still get that with this drive.
The TB2 version is out. I have one connected to my nMP right now. Model is ARC-8050T2.
You can buy it empty.
It works awesome.
It is super fast. >1250MB/s in RAID0 and >1000GB/s in RAID5.
I think these speeds exceed the real-world throughput of a TB1 bus, so if you plan on filling up a 8-bay box and xfer/stream big files, it might matter to you.
I'd be curious to see a comparo of the TB1 and TB2 boxes for random I/O. I think the internals are the same, so I suspect no diff or small difference-- so you might save some money (exsp if you prefer white color of TB1 versus black for TB2)
As I noted on another thread, the Areca 8050T2 in RAID5 is FASTER in both sequential AND random IO than my Apple PCIe SSD (1TB). That surprised me.
I bought mine direct and picked up locally (U.S. office is in Fremont, CA). Make sure you get the battery backup module if you want to (safely) maximize performance with cached writes. The box has 1GB of DRAM, so it can make a diff.
More info: http://www.cineraid.com/products/Areca_ARC-8050T2.htm
You can buy it empty.
It works awesome.
It is super fast. >1250MB/s in RAID0 and >1000GB/s in RAID5.
I think these speeds exceed the real-world throughput of a TB1 bus, so if you plan on filling up a 8-bay box and xfer/stream big files, it might matter to you.
I'd be curious to see a comparo of the TB1 and TB2 boxes for random I/O. I think the internals are the same, so I suspect no diff or small difference-- so you might save some money (exsp if you prefer white color of TB1 versus black for TB2)
As I noted on another thread, the Areca 8050T2 in RAID5 is FASTER in both sequential AND random IO than my Apple PCIe SSD (1TB). That surprised me.
I bought mine direct and picked up locally (U.S. office is in Fremont, CA). Make sure you get the battery backup module if you want to (safely) maximize performance with cached writes. The box has 1GB of DRAM, so it can make a diff.
More info: http://www.cineraid.com/products/Areca_ARC-8050T2.htm
I bought mine one week ago from OWC. They had it listed in their weekly garage sale email as a open box for $1179.00. I got the TB1 version. I populated it with 7 x 3tb WD reds and 1 4tb WD red. I config'd the 7 as a raid5 giving it 18tb and the 4tb I setup as a pass-through.
The raid5 gets me about 500mb/sec reads and 600mb/sec writes.
I use the raid5 for all storage needs and a massive Plex library and I use the single drive for cloning a very large Aperture3 library daily that is simply to painful to do to my Synology NAS box.
I had been using a Sonnettech Fusion5P which was a great unit back in the day but I have been running all my machines off of Internal and external SSD's for quite some time now and was growing weary with the slow esata connection of the Fusion.
The setup was drop dead simple and the quality of the box is top notch. It might not be as atheistically pleasing as the nMP or other machines but given it's performance I can accept a bit of a ugly duckling. When I was shopping for whatever was going to be my eventual purchase I looked all the usual suspects and when I compared as many of the features (that mattered to me) the Areca-8050 made the most sense (so glad I didn't buy Drobo 5d or the Pegasus units). A few weeks before I bought OWC came out with the Thunderbay array but that feel off quickly as it's not even in the same class of device.
I was pleasantly surprised at the time it took to initialize the 21tb to the 18tb array. It took about 5 hours. Other devices have taken 3 times that amount for just a fraction of the storage.
If there was one real gripe with the unit it would be It's nowhere near quiet. Don't get me wrong as it's not loud either. I have had some very loud array's before and this is not but, I would not plan on it sitting next to you to flank your Mac as you simply won't be happy. Locate the unit behind the desk or perhaps on the floor beneath it and all will be fine.
The raid5 gets me about 500mb/sec reads and 600mb/sec writes.
I use the raid5 for all storage needs and a massive Plex library and I use the single drive for cloning a very large Aperture3 library daily that is simply to painful to do to my Synology NAS box.
I had been using a Sonnettech Fusion5P which was a great unit back in the day but I have been running all my machines off of Internal and external SSD's for quite some time now and was growing weary with the slow esata connection of the Fusion.
The setup was drop dead simple and the quality of the box is top notch. It might not be as atheistically pleasing as the nMP or other machines but given it's performance I can accept a bit of a ugly duckling. When I was shopping for whatever was going to be my eventual purchase I looked all the usual suspects and when I compared as many of the features (that mattered to me) the Areca-8050 made the most sense (so glad I didn't buy Drobo 5d or the Pegasus units). A few weeks before I bought OWC came out with the Thunderbay array but that feel off quickly as it's not even in the same class of device.
I was pleasantly surprised at the time it took to initialize the 21tb to the 18tb array. It took about 5 hours. Other devices have taken 3 times that amount for just a fraction of the storage.
If there was one real gripe with the unit it would be It's nowhere near quiet. Don't get me wrong as it's not loud either. I have had some very loud array's before and this is not but, I would not plan on it sitting next to you to flank your Mac as you simply won't be happy. Locate the unit behind the desk or perhaps on the floor beneath it and all will be fine.
Mine from B&H (which I consider my own personal amazon.com), as the price dropped when the new TB2 unit was announced. Reviews of the Pegasus were littered with people complaining about early failure from one cause or another, and my experience with the speed of the second-gen Drobo left me wanting more (1).
I populated it with 4TB WD Reds, gave everything a workout as a RAID-0 for a few days, then switched to RAID-6. The unit is a bit slower in this configuration, but it is still faster than my internal SSD. It is not silent, but the noise at idle is not offensive and I forget that its there.
The fact that it shuts down cold when my Mac goes to sleep is both fantastic and disquieting. The OS never knows that the array went away - that is one clever device driver. All in all I consider the feature set and performance to be unmatched by any other device I have seen.
A.
(1) Although I have never been happy with the speed of the Drobo, I have to say that I have owned the second-gen unit since 2008, and as best that I can tell every byte that I wrote to it over the years was successfully read back out. For all its faults, it has been reliable.
I populated it with 4TB WD Reds, gave everything a workout as a RAID-0 for a few days, then switched to RAID-6. The unit is a bit slower in this configuration, but it is still faster than my internal SSD. It is not silent, but the noise at idle is not offensive and I forget that its there.
The fact that it shuts down cold when my Mac goes to sleep is both fantastic and disquieting. The OS never knows that the array went away - that is one clever device driver. All in all I consider the feature set and performance to be unmatched by any other device I have seen.
A.
(1) Although I have never been happy with the speed of the Drobo, I have to say that I have owned the second-gen unit since 2008, and as best that I can tell every byte that I wrote to it over the years was successfully read back out. For all its faults, it has been reliable.
For those of you who have ARC-8050T2, what kind of drives are you running? Toshiba, HGST, Seagate, WD? What models. WD Red seems like a popular choice but at 5400RPM, how much performance am I losing?
Anyone using strictly NAS drives? If so, what models and why?
http://www.custompcreview.com/articles/guides/selecting-best-hard-drive-network-attached-storage-nas/19177/
Anyone using strictly NAS drives? If so, what models and why?
http://www.custompcreview.com/articles/guides/selecting-best-hard-drive-network-attached-storage-nas/19177/
I am using Seagate 4TB NAS drives (8 of them) and am getting 950-1000MB/S in RAID5. I didn't do a ton of research, but I worried about the noise/heat/fan noise of 7200RPM performance drives and I worried about the premature erroneous "failure" that your linked article talks about. I had bad experience with a Drobo box dropping consumer WD drives, so figured I would try Seagate NAS drives (which are also a bit faster than WD RED drives).
So far so good, but again my research was not exhaustive. At about $175/each, I also felt that the price was decent.
So far so good, but again my research was not exhaustive. At about $175/each, I also felt that the price was decent.
Dumb question but I have to ask. Can I start with 4 drives in a RAID 5, then add more later, rebuild the RAID with additional drives without losing the existing data or once I build it, that's it.
If your question is specific to a specific Areca device, I can't help.
Many of the better RAID controllers do let you add drives to a RAID set - and even online - you can continue to use the volume while it is expanding.
This usually involves two "expansions".
- you have a partition that fills the volume - you add a disk to the volume and the RAID controller expands the volume so that there is "unallocated" free space at the end of the volume
- at the OS level you extend the partition containing the file system to add the unallocated space to the partition
Not a dumb question. You can add drives and expand the size of your RAID5 set, but then you'll need to reclaim this space by re-partitioning the HFS volumes in Disk Utility. All of this is non-destructive, although your data is at heightened risk during the actual rebuilding process.
Note that this is not as easy as the "Thin Provisioning" feature of Drobo (and higher-end enterprise storage systems) where the extra space automatically becomes available to the operating system.
I contacted Areca and their response was:
"all our raid products including 8050 support array expansion.
you can expande an exist raid5 volume with more capacity, no data lost.
the only limitation is only the latest volume can be expanded. so if you have multiple volumes, only the latest volume can be expanded."
"all our raid products including 8050 support array expansion.
you can expande an exist raid5 volume with more capacity, no data lost.
the only limitation is only the latest volume can be expanded. so if you have multiple volumes, only the latest volume can be expanded."
RAID5 performance with 2013 MacPro
Based on many good reviews, I bought the Areca 8050T2 (Thunderbolt2 version). Unlike the Thunderbolt1 cabinet, the T2 is not being discounted right now, but I felt the investment was worth it for the performance. Boy am I pleased!
Outfitted with 8 x4TB Western Digital enterprise-class drives (7200rpm), formatted for RAID5, I'm actually getting BETTER speeds from the Areca array than the built-in PCIe SSD in my new 8-core MacPro (2013 version) - 1035 MB/s write and 975 MB/s read. For comparison, the built-in PCIe SSD gets 935MB/s write and 925 MB/s read. That's REALLY impressive especially given RAID5.
If you're a fan of pretty light shows, the Areca won't disappoint either - especially during its (minute and a half) startup sequence. On the other hand, the LEDs are very bright which may be distracting to some people.
My only complaints are with the fan noise. I guess I've been spoiled for too long from the built-in fans in my prior 2009 MacPro. Starting up, the Areca sounds like a wind tunnel, but after its startup is complete, the fan noise drops to acceptable levels. But any workload raises the fan level to a noticeable (but not harsh) level.
But this brings up a final point that is critical for any RAID enclosure - power failure. Areca offers an optional battery backup unit for the 8050 (part number ARC-6120BA-T021) that you can order from their website for $150 (sometimes discounted). It doesn't keep the unit powered on, but it does protect the write cache for up to 72 hours. Without this backup, if you lose power during a critical write operation, it is possible to lose all data in certain striped RAID configurations (this is true of ANY RAID controller).
One final note - the Firmware Update does not work with Safari, although every other configuration does. I ended up successfully updating the firmware with Firefox.
Based on many good reviews, I bought the Areca 8050T2 (Thunderbolt2 version). Unlike the Thunderbolt1 cabinet, the T2 is not being discounted right now, but I felt the investment was worth it for the performance. Boy am I pleased!
Outfitted with 8 x4TB Western Digital enterprise-class drives (7200rpm), formatted for RAID5, I'm actually getting BETTER speeds from the Areca array than the built-in PCIe SSD in my new 8-core MacPro (2013 version) - 1035 MB/s write and 975 MB/s read. For comparison, the built-in PCIe SSD gets 935MB/s write and 925 MB/s read. That's REALLY impressive especially given RAID5.
If you're a fan of pretty light shows, the Areca won't disappoint either - especially during its (minute and a half) startup sequence. On the other hand, the LEDs are very bright which may be distracting to some people.
My only complaints are with the fan noise. I guess I've been spoiled for too long from the built-in fans in my prior 2009 MacPro. Starting up, the Areca sounds like a wind tunnel, but after its startup is complete, the fan noise drops to acceptable levels. But any workload raises the fan level to a noticeable (but not harsh) level.
But this brings up a final point that is critical for any RAID enclosure - power failure. Areca offers an optional battery backup unit for the 8050 (part number ARC-6120BA-T021) that you can order from their website for $150 (sometimes discounted). It doesn't keep the unit powered on, but it does protect the write cache for up to 72 hours. Without this backup, if you lose power during a critical write operation, it is possible to lose all data in certain striped RAID configurations (this is true of ANY RAID controller).
One final note - the Firmware Update does not work with Safari, although every other configuration does. I ended up successfully updating the firmware with Firefox.
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I find that I need Firefox to do anything useful with the web interface. I am disappointed, as thought people had learned not to write to a specific implementation of a browser and expect it to meet a standard.
On the positive side, I am always pleased when I do not have to install any software to get something running - it was plug and play on Mavericks.
A.
I would seriously advise anybody running this unit to
- buy the battery backup module
- run it at least in RAID6 mode
RAID5 is basically dead, since the arrival of 1 TB drives.
In the time it takes to rebuild a RAID5 with 1, 2, 3 oder 4 TB drives, another drive might fail (they're from the same series, usually....) and then your RAID is just a worthless piece of rotating rust.
AFAIK, Areca controllers are pretty fast at rebuilding the RAID in the event of a drive failure (RAID6 esp.).
- buy the battery backup module
- run it at least in RAID6 mode
RAID5 is basically dead, since the arrival of 1 TB drives.
In the time it takes to rebuild a RAID5 with 1, 2, 3 oder 4 TB drives, another drive might fail (they're from the same series, usually....) and then your RAID is just a worthless piece of rotating rust.
AFAIK, Areca controllers are pretty fast at rebuilding the RAID in the event of a drive failure (RAID6 esp.).