RAID 5 REBUILD extremely slow

[mxnerd]

My uncle's company is using a server I build with Intel Matrix Raid 5 with 3 disks - 137GB WD 10,000RPM SATA drives.

The company's location constantly has power outage problem. Even with UPS installed, the server constantly crashed since the power outage period is just too long and it usually happen in the midnight.

Every time the server crashed it rebuild the raid. However, it's extremely slow and took over 8 hours, during this time, the read/write is extremely slow, like 18MB/s for reading and 4MB/s for writing, usually less than that.

My question, what's your experience of Raid 5 rebuilding? Is it slow like this?

What's your opinion if I switch to RAID 1 with 2 disks, or RAID 10 with 4 disks? The slow speed of raid rebuilding is driving everyone crazy. Will raid 1 / 10 improve raid rebuild time?

And if I decided to use SAS drives, can they be used on SATA raid controller?? Or vice versa, using SATA drives with SAS controllers?

I'm interested buying this Fujitsu SAS drive.
http://www.newegg.com/Product/...x?Item=N82E16822116058.

If I do buy this drive, can i use it with the current motherboard (ABIT IP35 pro XE)? Or I have to buy a SAS controller to go with it? Which one would you suggest if it's around $400?

A lot of questions and appreciate your input. Thanks!

 

[RebateMonger]

Won't your UPS software shut down your server gracefully when the power dies? When power and battery backup fails, all the nice discussion about RAID and drive reliability goes out the door. I'd vote for keeping it as simple as possible.

I'd recommend switching to RAID 1 in your situation. And, yeah, RAID 5 rebuilds are slow. Also, be sure to either use a battery-backup on the RAID card or disable Write-back caching entirely. In your case, I'd disable Write-back caching.

I feel compelled to ask. You do keep ongoing backups of the array, too, right?

 

[Loreena]

Intel Matrix Raid is rubbish. Get rid of that setup ASAP. You would be better off with a pair of disks mirrored using Windows mirroring.

SAS disks will NOT work on a SATA line. You MUST use a SAS controller. You can, however, use a SATA drive on a SAS connector. Funny how that works.

That's an excellent drive you picked, the fastest mechanical drive out there and a good price. Pair it (or several) with a good controller and you will have a fast and reliable storage solution. This controller is within your budget and will fly compared to your IDE setup.

 

[Keitero]

I agree with Loreena here in saying that Intel Matrix RAID is complete crap. I suggest setting up a RAID 1 for your uncle using two big drives. Software is most cost effective and with RAID 1, you don't have to worry about any data lost if one drive dies. If you are looking for a redundancy with speed, then a RAID6 would be nice. Using an Adaptec 31205 PCI-E x8 controller tied with 4+ drives (either SATA or SAS) will do you good. I have a setup with 8x 750GB Samsung SpinPoint T drives in RAID5EE (RAID5 with hot-swap according to Adaptec). I get about 300MB/s reads and about 250MB/s writes. Burst of about 450MB/s. If they were SAS drives, I dare not think how fast it would be. ( I do have 4x Fujitsu 36GB SAS drives waiting to be installed).

 

[pugh]

I'm a home user of RAID and I wouldn't even trust my data to software RAID. A business using on-board RAID? Dump that junk and go hardware and do what the above poster advised.

 

[mxnerd]

To RebateMonger:

Yes, the UPS software supposed to work, since another machine using same software does work. the problem is that the SBS 2003 shutdown process probably took over 15 minutes. The battery ran out of juice before it can shutdown properly. I do plan buying bigger UPS and will disable some unused services on SBS.

Disabling write-back cache will slow down disk performance dramatically, so I'll think about using battery-backup on the RAID card.

I also do daily backup to another disk for 10 days worth of data.

To Loreena:

Thanks for the info on SAS/SATA. The controller you mentioned is low profile, I'll look for full height controller.

--------------

I did test for read/write performance before deciding Intel Matrix is good enough, both are over 100MB/s , just didn't know that the recovering performance is so bad for Raid 5. Yes, I think I'll dump the onboard controller and go with a mirror setup. Thank you all.

 

[Loreena]

Edit the registry key that tells windows to wait for end processes. SBS sets this to 600 seconds. Set it to 60 or 10 or less if you're brave. The box will shut down much faster.

 

[Viper GTS]

You can get decent SAS controllers for $400. Dell PERC 5's with battery backup can be had for half that or less. SATA drives work fine on SAS controllers, but not the other way around.

Rebuilds definitely take a long time, but rebuilds should virtually never happen. You need to work on ensuring that rebuilds only happen with hardware failure.

Viper GTS

 

[RebateMonger]

Originally posted by: mxnerd
To RebateMonger:

Yes, the UPS software supposed to work, since another machine using same software does work. the problem is that the SBS 2003 shutdown process probably took over 15 minutes. The battery ran out of juice before it can shutdown properly. I do plan buying bigger UPS and will disable some unused services on SBS.

Getting a bigger/better UPS is the FIRST thing I would do if you are having frequent long-term power outages. Something like the APC RS1500 will run longer than fifteen minutes.

Speaking of that, I don't have any SBS 2003 Servers that take fifteen minutes to shut down. In my experience, they take a couple of minutes to shut down. They take a long time to start up. The thing that takes a long time is Exchange Server, but that's hardly an "unused service".

 

[taltamir]

Make sure that the monitor and other peripherals are not plugged in the UPS, only the box itself. That way the monitor and modem and stuff turns off, but the box has juice for longer.
Also, get rid of the mobo based raid5.
Either buy a raid5/6 controller using hardware acceleration (300+$).
Or use RAID1 (you can use raid1 with the motherboard controller just fine... OR use the windows software mirror, that means setting raid to off on your mobo and doing it all in windows, also fine)

 

[mxnerd]

Thanks for all the tips, guys. I'll go through all the suggestions and make adjustments, cheers.