problem RAID-Disk Problem??

[grush]

I have a 4-bay iView RAID enclosure with a Jmicron controller using eSATA. I've been running RAID 5 with three Seagate ST3000DM001 3TB drives. I have been getting generally around 125-130 mbs transfer speed (shown by Windows 8. I just got my 4th drive (same kind). I backed up everything on it to my computer hard drive, installed the 4th disk, reset the controller and formatted. When I went to transfer my files back to the hard disk I was only getting around 20 mbs. I played around some more and started only getting about 1-3mbs transfer speed. I took the new disk out of the enclosure, reformatted it and was back to getting 125-130 mbs. I put the new disk in the enclosure again, checked the eSATA cables and started a transfer again. I was getting about 125 mbs. I thought that's good and the problem is solved, but when I looked a bit later on it was only transferring at about 20 mbs.

The only thing I can think of is there's a problem with the new Seagate ST3000DM001. Before I get an RMA and return the drive, is there anything I may be missing? Disk Manager shows the RAID array as a healthy drive.

Thanks very much for any help.

 

[P5-133XL]

Raid5 has by its very nature has poor write speeds but good read speeds. For sequential data transfers writes are limited to a single drive speed while reads can occur in parallel. Are you testing reads or writes?

You also have to worry about seek speeds. A raid5 volume acts like a single disk. Non-sequential data transfers (reads or writes) will be limited by seeks and that can cause data transfer to drop like a rock. Transfer testing on small or fragmented files can cause the above symptoms as well as I/O multi-tasking.

Next, possibility would be that you are testing the transfer rates while the RAID controller is trying to reconstruct a replaced drive which will also slow down your data transfers drastically until finished.

The above is true even if all the drives are perfect.

Generally if a drive is bad, it is marked bad and just not used in the array. That will slow down the array slightly but no worse than it was without the new drive. What you lose is not speed but rather the drive redundancy (because there is already a failed drive). If a single drive is failing but not yet labeled bad, the array will slow down drastically but you'll also hear repeated drive resets.

If you suspect a bad drive pull it and run Seagate's drive diagnosics on it as a single drive. If it passes, put the drive back and let the raid controller rebuild the raid array. When its done, defrag it and only when everything looks good test the data transfer by copying a very large single file to a separate drive/raid array.

P.S. Windows Disk Manager will only show a healthy vs. failed array if you are using Windows Software raid. It has no knowledge of what the Jmicron controller is doing. As far as Windows is concerned it is just a single drive and all single drives are healthy until they are missing or dead.

 

[Bozo]

Don't a lot of RAID controllers initialize the RAID array on the fly? This would really slow down the arrary until done.

 

[Stereodude]

Raid5 has by its very nature has poor write speeds but good read speeds. For sequential data transfers writes are limited to a single drive speed while reads can occur in parallel. Are you testing reads or writes?

Uh, not sure what you're talking about there. Write speeds can be just as fast as read speeds if the processor on the controller can keep up. You're certainly not limited to a single drive's write speed.

Here's 6 1.5TB 5400 RPM drives in RAID-5

The 8 of the same drives in RAID-6

8 2.0TB 5400 RPM drives in RAID-6

 

[grush]

Thank you P4-133XL for replying.

I'm looking at write speeds, since I'm almost always transferring files to the RAID, except in a case like yesterday where I backed up the RAID to my computer disk and reinitialized the disk after I installed the 4th drive. I bought the drives one at a time and used RAID 1 while I had 2 disks and then changed to RAID 5 at 3 disks. I never remember the transfers being that slow, although right now I'm just running the 3 drives at RAID 5 and I noticed for a short while the transfer was very slow until it sped back up. The drive is used almost solely for backup. I wait until I have a large amount of files to transfer and then copy them to the drive. Blazing speed isn't a big priority, but it was showing 21 hours yesterday after I installed the 4th drive to transfer about a gigabyte. I've never had USB 2.0 transfers that slow on my older external drives.

Like I said I initialized the drive so there was nothing to reconstruct, the drive was empty.

I agree with you about the bad drives. I don't hear any unusual noises from the drive or anything. I'm just wondering if there could have been some kind of discrepancy during the manufacture of the drive.

Thanks also for letting me know about Disk Manager and the health of the drives. I should have figured that one out. The JMicron RAID Manager that came with my drive is different than the one on the JMicron website and right now I can't find it.

I will download the Seagate diagnostics and run it singularly on the new drive. If everything is ok other than that, do you think I should just add the new drive again and run transfers in hope it will speed up eventually?

Thanks again for your help!

 

[grush]

Don't a lot of RAID controllers initialize the RAID array on the fly? This would really slow down the arrary until done.

Bozo: Thanks for your reply.

That's what I'm wondering also. If the drive is doing some "extra activities", and will speed up later.

 

[grush]

Stereodude:

Thanks for posting the tables. Makes my RAID look like crap even when it was running well. I'm sure it doesn't use the best controller. I got the enclosure from Newegg on sale for $99. However 130-150 MB/S is perfectly fine for my transfers. 1-3 MB/S is not. For awhile it was showing transfer rates in kilobytes.

 

[grush]

Ooops!

Oops...my bad...I meant to tranfer about a terrabyte, not a gigabyte. That would be even more horrible!

Blazing speed isn't a big priority, but it was showing 21 hours yesterday after I installed the 4th drive to transfer about a gigabyte. I've never had USB 2.0 transfers that slow on my older external drives.

 

[grush]

Wrong Again!

The correct amount showing 21 hours was about 100 gigabytes, 1/10 tb.

It's been a long night....I really need to take a nap.

 

[Mercutio]

It may very well be that the the disk controller's CPU is swamped with the extra parity calculations that come from the 4th drive. JMI controllers are very low cost parts and it just wouldn't shock me if that's the case. Those graphs were from a Perc5 or Perc6, right? That's not exactly an apples to apples comparison to anything from JMicron or SiL.

 

[Stereodude]

Those graphs were from a Perc5 or Perc6, right?

Yes, they are.

 

[grush]

You're probably right. I got the enclosure on sale at Newegg, and can't afford anything else right now. At the time I knew nothing about RAID controllers.

 

[Stereodude]

Don't get ahead of yourself. If you're sure it's not doing a background initialization, I'd suggest making a three drive array of the newest drive and two of the older ones and see if the 3 drive array returns to the original performance or if it's also slow. Then you'll know if you have a "bad" drive or if the RAID enclosure doesn't like using 4 drives.

 

[Mercutio]

The cheapo Rosewill/SiL 8-bay enclosure won't make an array with more than 5 drives, even in RAID1, and Intel Southbridge RAID doesn't offer the option to do RAID5 unless you're using a Server version of Windows for no good reason I can think of.
You may be better off with something like Windows 8 Storage Spaces instead.

 

[Stereodude]

...and Intel Southbridge RAID doesn't offer the option to do RAID5 unless you're using a Server version of Windows for no good reason I can think of.

Are you sure about that? I'm pretty sure as long as you have the R version of the chipset you can do RAID-5 regardless of the OS.

 

[Mercutio]

I've never bothered to try, but that was the gist of Intel's documentation a couple years ago.

 

[grush]

Well I tested it with Seatools for DOS, it seems like it's not compatible with Win 8. I just tested it against the 2tb Seagate drive in my computer. It was somewhat slower but that could be because of the controller and eSata. Anyway it tested out ok. I also installed and tested the drive with Hard Disk Sentinel which I kind of trust since it predicted the failure of my previous internal drive. It also showed everything ok in tests. When I put the four disks together in RAID 10 it was tremendously variable in speed sometimes up to 175 and sometimes it would stay around 50-75 and other times down below 5. Overall though the speed was acceptable for backup. Stereodude, I'll probably take your advice in the next couple days and set up a three disk array with the new disk and see if I get comparable speeds to what I was getting with the three old disks.