Which RAID-5 Card?

[m1ckran]

I've come accross a bunch of Western Digital drives at a very good joblot price (too good to miss) and I have a pc case capable of housing them.

My problem now is that I need a good, secure, fast PCI RAID-5 card that will handle eight 250Gb UDMA100 drives. I've looked around and read plenty of reviews but I still don't know which way to go. It looks as though RAID-5 on a PC is not viable or reliable. I'm leaning towards a mirrored array using a Rocketraid card but mirroring is so wasteful of diskspace.

Does anyone, I wonder, have such a card in their own system?

Any advice would be appreciated.

M1ckran

[tareek]

How about using Promise FastTrack SX4000 Lite (4 Ch, UATA 133, RAID 5, HW XOR, PCI 33MHz) cards, or, UltraTrak SX8000 (8 Ch, UATA 133, RAID 5, HW XOR) .
And i highly recommend, to make more air-holes on the casing for attaching multiple extra fans, to keep the hard-drives cooler, even before you start assembling everything inside .
If your overall cooling system is very very good and with right settings, then you may not need to do mirroring, but otherwise, mirroring is life saver .
- Tareek

[tareek]

if your drives are SATA, then how about using Promise FastTrak SX8300 (8 port, 3Gb/s (300MB/s), RAID 5, HW XOR, PCI-X 133MHz, 64bit) card ?
- Tareek

[m1ckran]

Thanks tareek, I'll check out those Promise cards. My drives are all PATA. I think that's why they're such a good buy. It looks as though everyone wants SATA now.

I've bought a case with six internal 3.5" bays and four external 5.25" bays so if I buy a Coolermaster 4in3 module, I will have space for ten hard drives plus DVD and floppy.

In addition to the Coolermaster module's 120mm fan, the case has cutouts for four 80mm fans (2 intakes and 2 exhausts) so I think I should be ok for cooling.

I'm not sure how long the power supply will last. It's 400 watts.

My big problem is with the reliability of PCI cards. I used to work in I.T. and we used SCSII Raid arrays costing thousands of pounds. They were fast and reliable (they never went wrong in 5 years coninuous use), but I'm not sure if the same can be said for non-professional cards. There is, after all, a BIG price difference!

Do you have experience of the cards you mention?

[Pookie]

I had a raid 5 array unit lose TWO drives recently. All of the drives were WD 250MB. My only advice is to frequently back up your important data.

[tareek]

out couple of setup done by me, most of the time i had to (in the end), get rid of other cards due to various reason, but promise was very reliable . never lost cards . but drives only . then i've put my attention on cooler air flow , PSU . now whole setup are very very reliable . if you once in a while, also remove dust, replace fan, etc . used SX4000 Lite and 2 channel versions mostly and alaways configure mirror setup . i prefer to use 1 fan for max 2 drives only . if it says 400W, may be it is actually 300W or less , depends on what manuf./ it is and where you bought it from , etc . suppose for 10 drives, 300W / 10 = 30W per drive . usually at heavy r/w mode , older drive consume ~14W, newer ~9W (approximately) . and recent drives uses more lower power . during startup they consume / need more . i prefer to double up the r/w usage watt, so its almost ~28W (older) / ~20W (newer) . so it is good for 10 hard drives, for reliable operation (with continuous running mode/setup) .

[m1ckran]

Thanks pookie and tareek, especially for your power supply comments. The case and power supply are Chinese. The labels suggest a true 400w supply. I will not be using the power outlet socket.

I've borrowed a used Rocketraid 454 from a local dealer so I can try it out. I know it's not in the same league a a Promise but it will give me some idea of what to expect.

I connected all eight drives and configured them as two separate stripe-sets of four drives each and did full formats in Windows. The first set wrote a 1Gb file (a VOB file from DVD Shrink) in 21 seconds but the second set took 32 seconds for the same file. Strange. I know there's no redundancy there but, I suppose, I could treat the second set as a backup by manually copying from one to the other.

I'm now builing a Raid5 array using 7 drives with a spare. From what I've learned, I don't expect good performance but I need to compare the results. Then I will try mirrored arrays for comparrison. I also want to find out how the arrays cope with losing a drive.

It looks as though it's going to take about 10 hours to build the array so I'll have to be patient. I'll keep you informed. Thanks again.

[tareek]

With a 4 Ch RAID card, i prefer to use RAID 10 configuration/setup .
RAID 10 :
HDD A HDD B HDD C HDD D
Strip 1A(1) Strip 1A(2) Strip 1B(1) Strip 1B(2)
Strip 2A(1) Strip 2A(2) Strip 2B(1) Strip 2B(2)
Strip 3A(1) Strip 3A(2) Strip 3B(1) Strip 3B(2)
Strip 4A(1) Strip 4A(2) Strip 4B(1) Strip 4B(2)So, four 250GB drives will become one 500GB drive in R10 (RAID 10) setup .
RAID 5 (with 4 drive) / R5(4) :
HDD A HDD B HDD C HDD D
Strip 1a Strip 2a Strip 3a P(a)
Strip 1b Strip 2b P(b) Strip 4b
Strip 1c P(c) Strip 3c Strip 4c
P(d) Strip 2d Strip 3d Strip 4dSo four 250GB drives will become one 750GB drive in R5(4) setup .
RAID 5 (with 3 drive) / R5(3) :
HDD A HDD B HDD C
Strip 1A Strip 1B P(1A,1B)
P(2B,2C) Strip 2B Strip 2C
Strip 3A P(3A,3C) Strip 3C
Strip 4A Strip 4B P(4A,4B)So three 250GB drives will become one 500GB drive in R5(3) setup .

Approximately...
R1(2) is better in avg reads than a single/JBOD drive .
R5(4) is ~ 22% better in avg reads than R5(3), or R1(2) .
R5 can take advantage of many features found in these 4 ch RAID card .
R10(4) is ~ 200% better in avg reads than R5(3), or R1(2) .
R0(4) is ~ 378% better in avg reads than R5(4) .
R0(4) is ~ 400% better in avg reads than R5(3) and ~ 200% better than R10(4) .
But loosing even 1 drive in R0 will cause all data to be lost in any R0 , so fault tolerance is 0 .
R5 can withstand 1 drive failure . R10( with 4 drives) can recover from upto 2 drive failure if they are in same pair .

on-the-fly / hot-swapping / hot-replacement is possible on R1, R10, thus 0 downtime, and lowest rebuild time . it works when each channel is used for 1 drive only . drive lost in other array config will cause downtime and rebuild time both .

With 7 drive (each 250GB) in a R5 array config, your final drive size is 1.5TB ! super great, but, you could have put all 8 drive for 1.75 TB (Terra Bytes) . in that config, if only 1 drive is lost, you'll face downtime and rebuild time .

may you should buy or look for good deals on more (similar) WD 250GB drives, starting from now .

[tareek]

never liked R5, so, never lost all data . I'm sure Pookie lost all data in that raid 5 array, because of 2 drives were lost , unless it was 1+5 setup ! and agree with Pookie on "backup", constant scheduled backup is very very good thing as our goals are, redundancy & performance . i remember looking for better deals and buying lots of similar hard drives for imergency situation / drive failure . but when the array were working almost flawlessly, then i had to use those as single drive in different PCs .

[m1ckran]

Wow, tareek,

I didn't expect such a level of detail. Your replies must take ages to prepare! Thank you.

I tested my 7-drive Raid5 array. It took about five hours to build. Read performance was about the same as my onboard UDMA133 controller which I think is Ok considering the Raid array uses UDMA100 drives. Write performance was quite slow: 1min 21sec to write a 1Gb file against 21sec for the Raid0 test.

I agree that I could have used all eight drives in the array, but I used one as a spare for my disaster test. I removed one of the array drives and rebooted. The controller reported a broken array and started to rebuild itself using the spare. It took over six hours but it worked.

Raid5 gives me a huge drive to look at and appears to be secure if ony one drive fails. The downside is that write performance is slow and rebuild time, after losing a drive, is poor . I'm guessing that the rebuild time will increase proportionally with the amount of data stored.

Although the huge drive is tempting, I think your advice is good. Slow writes would probably get on my nerves, and disaster downtime is far too long. An interesting test but I think I'll avoid Raid5.

Next I'm going to try Raid10. I'll keep you posted.

m1ckran

[tareek]

many many thanks to you, for keeping us informed . please also mention the motherboard's manuf. & model and the processor type & speed, amount of RAM & speed & type, etc to get a better idea on your config which took 5 hours to format a 1.5TB NTFS RAID array drive . thanks .

[m1ckran]

Sorry for the delay - I've been having fun.

The Raid5 array collapsed and I lost everything. So I creating a striped-mirrored array which, on testing with a huge copy, worked quite well. But when I switched on the next day, I again had problems and lost the entire mirrored array!

It turned out that one drive is defective! Perhaps a redundant array only works if it's sound when created. I'm gettting a replacement drive, then I'll try again, but I'm now leaning towards two striped arrays (no mirror and no parity) with manual copying from one to the other for backup purposes. From my experiments so far, I think this will give me the best write speed.

[m1ckran]

Thanks, people, and sorry for my delay in getting back.

On the UK, the RAID5 cards suggested are either ridiculously expensive, no longer available, or both.

After testing, I find that Highpoint RocketRaid cards neither go like rockets, nor provide a stable raid array. I was never able to retrieve data after I sabotaged an array by removing a drive.

The only fast, reliable, affordable cards I can find are the Revo64 variants, but they use SATA drives only.

I have decided to use two cheap EIO/Innovision cards to provide two striped arrays, using the second array as a manual backup device for the first.

Cost effective and workable!