SE, RE, or RE2 Western Digitals for RAID

[FireFoxx74]

Hi all,

Has anyone run Western Digital SE drives in a RAID array? WD warns that the SE drives have a long error-recovery time, which may cause the RAID array to drop the drive, but has anyone actually had that happen?

I am looking at purchasing a Asus M2N32 WS Pro board (6xSATA), and some 500/750/1Tb drives for RAID, but the cost between SE and RE2 is nearly £60 (per drive!).

Any feedback appreciated.

[laguz1]

RE2 is more enterprised based, it has NCQ, higher MTBF, and some other features built for RAID setups, but honestly...if you run your computer normally, i don't think that long error recovery time and "dropping" out of the array means much to a normal user.

I have a SE WD, one of the orig. 250gb 8mb cache SATA150, ones and i usually run my computer 24/7...about 2 years so far...and no issues.

I'm guessing you're probably safe running SE's in RAID.

Oh, sorry, but i haven't run hd's in RAID, but just tossing out my opinion

[tibetan mod king]

Hi all,

Has anyone run Western Digital SE drives in a RAID array? WD warns that the SE drives have a long error-recovery time, which may cause the RAID array to drop the drive, but has anyone actually had that happen?

I am looking at purchasing a Asus M2N32 WS Pro board (6xSATA), and some 500/750/1Tb drives for RAID, but the cost between SE and RE2 is nearly £60 (per drive!).

Any feedback appreciated.

I run a number of Western Digital Enterprise drives, from the 74GB Raptors up through the 500GB RE2s. All my RAID arrays are based on various 3ware cards.

If you run a 3ware card, the "RE" is absolutely critical. If not an "RE" drive, the drive BIOS must be RAID controller compatible. Many consumer drives will not respond to the 3ware fast enough and the 3ware will drop the drive out. So you will either see a degraded array or no array depending on your RAID setup. This will happen even if you are copying a lot of files, running chkdsk, etc. It doesn't take much. With all the "RE" drives I have used, I have never had a drive drop out due to RAID controller / drive interaction issues.

Other than Western Digital, I've had good luck with Barracuda 7200.10 drives (non-ES actually, many BIOS versions work just find with the 3ware). These Seagate 7200.10s have actually more reliable than my WD 7200 rpm drives, but not as reliable as the Raptors. The "ES" and "ES.2" drives from Seagate also feature time limited error recovery, similar to Western Digital.

The consumer model Hitachi 1TB (7K1000) does not work with 3ware well. But the enterprise model (A7K1000) allegedly does. I didn't order an A7K1000 as the basic drive design runs very hot. It is a fast drive, but for 1TB something like the 3 platter Samsung will probably be the overall winner (which may have issues with RAID as other Samsungs have had in the past).

Outside of the 3ware world, I don't know what will/won't work. You will need to look at how each RAID controller/driver deals with drive access, response time, etc.

At least in the US, Western Digital warranty service on the Enterprise drives is not very fast. It will take 3-4 weeks to get a replacement drive under warranty. You will also have to hassle them once or twice. Hence think "cold spare" as well as "hot spare".

Lastly, I believe on the 3ware website they keep a list of all validated drives. The "SE" drives are on the list. As is a comment "RE is recommended". If a drive works with a 3ware, it will likely work with less demanding RAID controllers/drivers as well.

Okay, one more thing. If you are running RAID, do not buy drives that are brand new to the market. Wait for a few batches so they can get the manufacturing bugs out. This usually takes 6 months (for example, my 7200.10s were purchased after Seagate fixed the early noise/heat issues. The ones I have are really good drives. Fast, quiet, and reliable.) And of course, if you buy drives in quantity make sure to allocate drive serial numbers appropriately amongst your RAID arrays so the probability of coincident failure is minimized.

For your board, the RAID is really host raid. The chance that host raid will drop out with a consumer drive is low. The drivers used are basically the same drivers as for normal non-RAID usage. So the drivers are aware of long time-outs. You should be able to go ahead and get consumer drives for your consumer RAID. Just keep in mind that consumer drives will not necessarily work well on a hardware RAID controller if you ever decide to go that route. And when you get data corruption errors on your consumer RAID due to lack of data scrubbing, well, at least you know the issues when you want to move to better RAID and/or a better file system such as ZFS which can do data scrubbing.

Okay, another one more thing. Beyond working better with your RAID controller, "Enterprise" drives usually have much better bit error rates. Much better can be an order of magnitude.

For instance, the Barracuda 7200.11's BER (bit error rate) is an order of magnitude worse than that of the Barracuda ES.2, which boasts one permanent read error for every quadrillion bits read.

What that means in practical terms is that, with the 7200.11 drives, a read error is statistically certain for every 12TB read. With a big array, this means you will get data corruption on every full array rebuild.

With the more reliable ES.2 drives in place, the error would occur after the drives read 120TB.

So for ANY drives you buy, take a peek at the bit error rates and see how they compare. These error rates are much more important if your RAID controller / file system does NOT do media/data scrubbing.

Cheers

[Nick Geraedts]

I run a number of Western Digital Enterprise drives, from the 74GB Raptors up through the 500GB RE2s. All my RAID arrays are based on various 3ware cards.

If you run a 3ware card, the "RE" is absolutely critical. If not an "RE" drive, the drive BIOS must be RAID controller compatible. Many consumer drives will not respond to the 3ware fast enough and the 3ware will drop the drive out. So you will either see a degraded array or no array depending on your RAID setup. This will happen even if you are copying a lot of files, running chkdsk, etc. It doesn't take much. With all the "RE" drives I have used, I have never had a drive drop out due to RAID controller / drive interaction issues.

I can't really agree with this - I've got a 4 drive array built on a 3ware 9650SE-8LPML card using WD5000AAKS drives, and I've had one scenario where the array kept degrading, but that turned out to be due to a faulty cable. Since I replaced the cable, it's never happened.

The TLER feature of the drives is most critical in situations where you have a lot of I/O operations. If the drive does encounter an error, but has a lot of I/O operations in it's queue, then it may be dropped before it can repair the drive. The RE and RE2 drives use TLER to hide the fact that a disk error has occured, and it gives the drive a chance to fix the problem.

The SE16 drives will be fine for your home array. If you were building a mission critical storage server for a business, then I'd suggest RE or RE2 drives.

[tibetan mod king]

I run a number of Western Digital Enterprise drives, from the 74GB Raptors up through the 500GB RE2s. All my RAID arrays are based on various 3ware cards.

If you run a 3ware card, the "RE" is absolutely critical. If not an "RE" drive, the drive BIOS must be RAID controller compatible. Many consumer drives will not respond to the 3ware fast enough and the 3ware will drop the drive out. So you will either see a degraded array or no array depending on your RAID setup. This will happen even if you are copying a lot of files, running chkdsk, etc. It doesn't take much. With all the "RE" drives I have used, I have never had a drive drop out due to RAID controller / drive interaction issues.

I can't really agree with this - I've got a 4 drive array built on a 3ware 9650SE-8LPML card using WD5000AAKS drives, and I've had one scenario where the array kept degrading, but that turned out to be due to a faulty cable. Since I replaced the cable, it's never happened.

The TLER feature of the drives is most critical in situations where you have a lot of I/O operations. If the drive does encounter an error, but has a lot of I/O operations in it's queue, then it may be dropped before it can repair the drive. The RE and RE2 drives use TLER to hide the fact that a disk error has occured, and it gives the drive a chance to fix the problem.

The SE16 drives will be fine for your home array. If you were building a mission critical storage server for a business, then I'd suggest RE or RE2 drives.

As I said, "If not an "RE" drive, the drive BIOS must be RAID controller compatible." It so happens that the WD5000AAKS is specifically validated with the 9650se with firmware 11.02N11. Using a validated drive is of course fine. The bit error rates on the WD5000AAKS and the RE edition of the drive are the same, too.

For other drives, the OP should check compatibility ahead of time, especially when voyaging into the rather indeterminate world of host RAID.

[FireFoxx74]

Thanks for the advice.

I really do like the look of RE and RE2, especially the more recent ones which give the Raptors a challenge. It's the £60 difference per disk which is the concerning part.

[tibetan mod king]

Thanks for the advice.

I really do like the look of RE and RE2, especially the more recent ones which give the Raptors a challenge. It's the £60 difference per disk which is the concerning part.

The RE/RE2 drives do not offer any overall performance gains vs. the non-RE/RE2 versions of the same drives. However, they generally work better in the RAID environment and do offer longer warranties.

Remember, if a non-RE/RE2 drive is validated for RAID usage using your controller/driver, that is fine. And given the big price difference, you may be better off using that money for a hot spare and/or cold spare vs. RE/RE2 drives.

Also, in the real world, the Raptor is a very fast drive. The RE/RE2 drives do not match up except in artificial benchmarks. For two machines I use a Raptor RAID1 array for the OS and swap and use an RE/RE2 RAID1 or RAID10 array for data. I do not use RAID5 or RAID6 due to the high costs of data recovery for a failed RAID.

In the 3ware world, you may wish to invest in a battery back up unit (BBU) for the 3ware controller itself. Money spent on the BBU and spares is very effective risk management. My data has been saved a number of times via the BBU's write journaling and the 3ware's automatic use of a hot spare to rebuild a degraded array.

Personally, having seen many people get burned using host RAID, I would spend less on drives, but get a 3ware card for SATA RAID. Use less expensive but validated drives on the 3ware and you end up with something that is fast and reliable.

[jackylman]

...with the 7200.11 drives, a read error is statistically certain for every 12TB read.

I'm nit-picking, but it's not certain that you'll get an error at the exact rate given my the manufacturer any more than it is that your drive will fail at its rated MTBF.

EDIT: Okay, you said "statistically certain", so I guess that's what you meant. (I just found that term a bit ambiguous).

[matt_garman]

Has anyone run Western Digital SE drives in a RAID array? WD warns that the SE drives have a long error-recovery time, which may cause the RAID array to drop the drive, but has anyone actually had that happen?

I am looking at purchasing a Asus M2N32 WS Pro board (6xSATA), and some 500/750/1Tb drives for RAID, but the cost between SE and RE2 is nearly £60 (per drive!).

What operating system will you run? I use Linux software RAID (md) for my big storage needs. I originally built it using four 400 GB RE2 drives. I recently upgraded to four 750 GB SE drives.

First thing to note: I think the RE2 drives have a five year warranty, versus the SE's three year. But even in three years, I know I'll be ready for another upgrade.

I never took the time to look at how the drives are manufactured, but the 400 GB RE2 drives all run cooler by about five degrees Celsius (compared to the SE drives). This could be explained by a difference in the number of platters though. On the other hand, the RE2 drives definitely feel more substantial---they are heavier, and the case looks more rugged, like the case of my Raptor. I actually dropped one of the RE2s on a hardwood floor once; still works fine.

My personal recommendation is to either use Linux software RAID or buy a dedicated RAID card. The BIOS-based or firmware-based RAID implementations are junk. For personal/home use, or even lighter-duty commercial applications, the money you save with Linux software RAID makes it extremely appealing. Some of those true RAID cards cost over $500, and you you could buy two more 1 TB drives with that money, and use it in RAID6 or RAID10, or have a hot-spare, etc. Unless you need to get really fancy, Linux software RAID will do almost anything the dedicated hardware cards can do.

[tibetan mod king]

Has anyone run Western Digital SE drives in a RAID array? WD warns that the SE drives have a long error-recovery time, which may cause the RAID array to drop the drive, but has anyone actually had that happen?

I am looking at purchasing a Asus M2N32 WS Pro board (6xSATA), and some 500/750/1Tb drives for RAID, but the cost between SE and RE2 is nearly £60 (per drive!).

My personal recommendation is to either use Linux software RAID or buy a dedicated RAID card. The BIOS-based or firmware-based RAID implementations are junk. For personal/home use, or even lighter-duty commercial applications, the money you save with Linux software RAID makes it extremely appealing. Some of those true RAID cards cost over $500, and you you could buy two more 1 TB drives with that money, and use it in RAID6 or RAID10, or have a hot-spare, etc. Unless you need to get really fancy, Linux software RAID will do almost anything the dedicated hardware cards can do.

This is good advice. BIOS/Host RAID is asking for problems. Both Linux software RAID and true hardware RAID cards are used in the business world -- so there is accountability. And when there is accountability, you will find quality and reliability.

The 3ware card is a good choice if you don't want to get into Linux details. Everything is run from a web-based admin UI (command line is available if you need it, too).

In Linux software RAID, you will need to know enough Linux to setup regular media scrubbing and other details of how the RAID works. The plus of Linux software RAID is that it removes dependencies on third party drivers. Even though 3ware, LSI, Adaptec and others do have drivers built into the kernel, these drivers vary as the version of the kernel you are using varies.

So, like most things, there are tradeoffs to be made.