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PowerEdge Slow eSATA

Posted on 2011-09-26
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Last Modified: 2012-05-12
We just installed new eSATA backup hardware on our server in the hope of better speed. However, the speed we get is exactly the same as with the old USB 2.0. What is it about this server that limits the backup speed to 6 MB/s? Thank you experts for helping.

Dell PowerEdge SC430, with SBS 2003 (Server 2003 has latest updates)
Vantec UGT-ST400 card 3 Gb/s (SATA II), on x1 PCIe
Internal OS Drive connected to onboard SATA I controller
Internal DATA Drive (SATA II) connected to internal Vantec card connection
External Iomega drive 34527 (eSATA II) 3Gb/s connected to eSATA connection on Vantec card

Backup 1 (ntbackup) from OS drive to external drive- 6 MB/s, should be 3 times faster at least
Backup 2 (ntbackup) from DATA drive to external drive- same 6 MB/s, should be 6 times faster
Note: during backup there is no other activity on server.

What is it about this server that limits the backup speed to 6 MB/s?
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Question by:campinam
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by:klodefactor
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With the system idle, try backing up from OS to DATA.  That eliminates the external drive case but uses the Vantec controller.

Backup speed also depends on the files you're backing up.  If you have zillions of small files, the backup operation will be slower.   Have you tried a simpler test?  Create a single large file (e.g. 1GB) on the OS drive and try the following copy operations:
- from OS to external
- from DATA to external
- from OS to DATA
By the way even with a USB 2.0 drive, a single large file should get 20+MB/s read/write speed.

Also, why do you expect the eSATA drive to be only three times faster?  What is the model number of the external hard drive?  For any modern SATA HD connected via eSATA, you should see speeds anywhere from 60MB/s to 100+MB/s.

--klodefactor
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by:campinam
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IMPORTANT:
== the backup speed of THE SAME data remains THE SAME as on previous USB 2.0 backups ==

>>why do you expect the eSATA drive to be only three times faster?
just considering all possible factors like small files, etc. (not really the case) I'd be happy with a three times speed! But no, the speed is THE SAME as on USB2, as if USB  was also limited by the same bottleneck. Could this be related to the PowerEdge or the x1 PCIe?
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by:klodefactor
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I don't think it's the backup device or bus.   As I mentioned, even with USB 2.0 you should have been getting 20+MB/s, not 6MB/s.

The most likely culprit is ntbackup combined with the number/size of files you're backup up.  Have you been able to try the large, single-file test I suggested?

--klodefactor
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by:campinam
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Not yet, but let's put it this way... We used THE SAME data as with USB, shouldn't we have observed some speed increase, no matter how small? So it's not the files...

Additionally, backup 1 runs with verification, backup 2 without, and still the same dreadful 6MB/s speed!

Some bottleneck limits speed in all cases to the same 6MB/s. But which is it, the bottleneck?
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by:klodefactor
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Possible bottlenecks for your backups:
- slow file system (by design, or due to heavy load)
- large number of small files
- poorly written application
- slow RAM, or all RAM in use with heaving paging activity
- slow CPU, or CPU overloaded
- slow system bus
- problem with USB hardware/driver (USB scenario)
- problem with expansion card (eSATA scenario)
- problem with external drive enclosure
You wouldn't necessarily see a speed increase even with faster storage.  If the limiting factor for backup speed is the software + mix of files, it doesn't matter how fast the storage is.  You could be storing to an 8Gbps Fibre Channel SAN with enterprise SSDs in a RAID0 configuration, but if the data only arrives at 6MB/s, it will only be written at 6MB/s.

I think we'll know more after that large-file copy test.

--klodefactor
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by:klodefactor
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I forgot to point out again that 6MB/s is *slow*, even for USB 2.0.  If the drive was the bottleneck, you should have been getting 20+MB/s.  This is what makes me think you need to look elsewhere.

--klodefactor
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by:campinam
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Just learned that SATA controller on PowerEdge could be in PIO mode (which severely limits speed) . How do I make sure the SATA controllers (onboard SATA I and Vantec card SATA II) run at nominal speed? Drivers, BIOS settings?

Experts, anyone fixed this before?
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klodefactor earned 500 total points
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Where did you see the report about PIO?  PIO (and DMA) are meaningless for SATA drives; they use a completely different communication method.

I don't want to be rude, but I'm not certain I can do much more for you until you check the performance of your hard drives using something other than your backup software.  If you prefer not to create and copy a large file as I described above, you should run hard drive benchmarking software in order check performance.  You could try Passmark's "Performance Test" (http://www.passmark.com/products/pt.htm) or HDTune (http://www.hdtune.com/).

Really, the cluster of symptoms you describe points squarely at your backup software + file mix, but we have to confirm that before proceeding.  That's why the next logical step is an independent check of drive performance.

--klodefactor
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by:campinam
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Sorry for the delay - didn't have much access to the server - but now we know it's ntbackup the problem, so you were right. Thanks a lot.
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