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Slow Disk to disk backup speeds over gig links

Posted on 2005-04-08
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Last Modified: 2013-12-01
All,

I have set up a backup to disk job (from backup exec, using remote agents) over gig links (The NAS box is a gig card, the server I wish to backup has a GiG NIC Card and the switch im going through is a gig switch) and am only getting 131MB/Min throughput....? its taking 15 mins to do 2GB. This is normal speeds....I've set the NIC card in backup exec that it needs to use, ive upgraded the drivers for the NIC cards...

Anyone any ideas?

Cheers
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Question by:credmood
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by:rindi
ID: 13738373
Are you just doing file backups? is it a database backup, ie SQL Server or Exchange Server? during backup, disable your antivirus software.
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Expert Comment

by:Lee W, MVP
ID: 13738744
What size are the files?  Small files always backup slower than large ones... and if these are 5-25K (or so) files then your throughput sounds about right.
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Author Comment

by:credmood
ID: 13739191
Its just file backups, in fact its just a test on the C drive of a new system Ive just built. So its doing a system state and the system C partition....We've got the gig stuff in, so the backups will be quicker, I work out that u should (in theory) get about 400 Gig an hour throughput on a Gbps ethernet backbone.
Am I missing a trick here....?

Is it worth setting the MTU size on the NICS to 9000 ....?  Also is it worth copying stuff across the links and outputting a log file to tell me what the throughput is on that?
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Expert Comment

by:vonskie
ID: 13740677
I have seen this many times before make sure the network card is not set to auto (duplex or speed) nail it to full and the speed desired assuming that gig network card is hooked to a gig switch and so on... also make sure you have the latest drivers and updates for the network card and tape backup software...
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Assisted Solution

by:Lee W, MVP
Lee W, MVP earned 400 total points
ID: 13742399
I'll say again, small files backup slower.  And in a system state backup, the files are generally fairly small.  Each file must be located on the disk, opened, read, closed, move on to the next file.  This is a slow process.  Test this.  Copy 1000 10K files and 1 10 MB file seperately.  You'll see what I'm talking about.
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Author Comment

by:credmood
ID: 13742748
Yes, I get your point, Im gonna do a backup on just *data* and get the log reading. I guess the test im doing is not indicative of a mainly *data* backup....which is what it will be, i.e I have 100 GB of in the main *larger files* to backup..

Cheers leew, sorry for repeating myself

Ill also do what vonskie has suggested re the auto speeds (btw I have installed the latest NIC drivers and its a Disk to disk im dong not a tape style)

However, does anyone have an opinion on whether I should change the MTU? would i get any benefit ? I assume you must get something if the frame packet is a larger *chunk*
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by:rindi
ID: 13742770
You could test the speed of your lan by copying data by hand, without using veritas (Also copy a large file), and as I said earlier, disable AV software. This is very often the cause of slow backup speeds. After all the data should have been screen before it got on the server, so disabling the AV software before backing up should not be a problem.
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Author Comment

by:credmood
ID: 13743065
Yes, I was gonna use a robocopy to chuck some stuff across, however can I choose which NIC to use, when doing it *manually* ?
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by:rindi
ID: 13743101
You could try using the URL of the destination server in the form \\IPAddressOfNICYouWantToUse\Share. I've never tried that but maybe it works.
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Author Comment

by:credmood
ID: 13746358
rindi, a UNC on the correct NIC does work....

However the robocopy log file shows me a throughput of 388MB/MIN on 1GB worth of test files, which by my calculations is NOT gigabit speeds...I took the switch out of the *loop* and just cabled between the NICS. I calcualte that *theoratically* i should get 7500MB/MIN through Gig cards..I know thats never gonna happen (size of files, as leew explained to me). So on a 100Mbps network you should get 750MB/MIN, which is closeish to the throughput that Im getting (again 750 is a max, something u'll never get) but the point is 384 MB/MIN is condusive to a 100Mbps link....

As the switch is out of the equation I am thinking that its gotta be something to do with the cards (or the cable, I am using CAt5E, but Im sure thats fine so Im going for the cards being the problem)..Broadcom NetExtreme...
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by:rindi
ID: 13746377
Then it could also be the NIC drivers, and check your BIOS, maybe you have to set some Bus mastering for those nics.
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by:andyalder
ID: 13746572
How many disks of what speed are in the source array you are copying from? At only 6.4MB/s it sounds like there is only one or two disks in the array. You need quite a few disks in both the source server and the backup server to get anywhere near gigabit speeds.
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Expert Comment

by:vonskie
ID: 13748288
Here is something worth reading about cables, speeds and etc...


 What is the difference between CAT5, CAT5e, CAT6, CAT7...
The Simple Answer:  
CAT5 is rated to 100M
CAT5e is rated to 350M
CAT6 and CAT6e is rated to 550M or 1000M depending on your source
CAT7 is supposedly rated to 700M or presumably 1000M

Today there is no approved CAT6 or CAT7. While some folks are selling products they call Level 6 or 7, there aren’t even specs for them, making CAT5e the best available option.  CAT6 cable is being made with 23 guage conductor wire as opposed to the slightly smaller 24 guage for CAT5e and also has a separator to handle crosstalk better.

Both CAT5 and CAT5e have 100 ohm impedance and electrical characteristics supporting transmissions up to 100 MHz. The differences between CAT5 and CAT5e show in all aspects of performance: capacitance, frequency, resistance, attenuation, and NEXT.  CAT5e components were designed with high-speed gigabit Ethernet in mind. While CAT5 components may function to some degree in a gigabit Ethernet, they perform below standard during high-data transfer scenarios.  CAT5e cables work with ATM and gigabit speed products.  Simply, if you are using a 100Mbps switch, get CAT5e cable instead of CAT5.

CAT5e is formally called ANSI/TIA/EIA 568A-5 or simply Category 5e (the e stands for ‘enhanced’).  CAT5e is completely backward compatible with current CAT5 equipment. The enhanced electrical performance of CAT5e ensures that the cable will support applications that require additional bandwidth, such as gigabit Ethernet or analog video.

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Expert Comment

by:vonskie
ID: 13748300
Category 6 or for that matter even cat5e patch cords are precision products, just like the cables and the connectors. They are best manufactured and tested in a controlled environment to ensure consistent, reliable performance. This will ensure interoperability and backward compatibility. All this supports patch cords as a factory-assembled product rather than a field-assembled product provide consistent performance and better interoperability than their hand crimped & non-moulded counterparts.
It should be also noted that hand crimped patch cords are fitted with boots and sold as factory crimped cords which result in unnecessary increase in retransmission loses, Also the use of latch protector is experienced in working in high density environments where it helps to add & remove existing patch cords with ease.
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Assisted Solution

by:vonskie
vonskie earned 400 total points
ID: 13748319
Another thing to consider are the patch panels rated as cat5 or cat5e?
I have seen some cat5e cables being punched into standard analog phone blocks... and it causes problems datawise...
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Author Comment

by:credmood
ID: 13750628
andyalder, there are 6 disks in the source server (ultra160 SCSI) in a RAID 5 config, the backup server is also a RAID 5 but over 4 disks, however the NAS box is IDE, however thats rated to 100MB/sec. Again I know you wont get that, but I cant see that as the problem...I know it would be better to have a scsi NAS box, but we got this NAS box gratis from a company acquisition and budgets dont allow me to purhase one, im trying to make the best of what we have
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Author Comment

by:credmood
ID: 13750654
vonksie, I just have them plugging into a switch, Im *bypassing* my patch panel..as they are all servers that I have locked away in my server room. However I am using CAT 5e cable, Ill purchase some CAT6 cable, even if it isnt approved and see what I get. I did notice that I wasnt get the gig link light on the switch, its a HP procurve 2724 24 port autosensing gig switch.
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Expert Comment

by:rindi
ID: 13750696
Did you try manualy setting the speed to 1gig, Full duplex on both the swith (for those ports connected to the servers) and also on the NIC of those servers. I take it that the switch is managed and you can manually set the speed?
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Author Comment

by:credmood
ID: 13751217
this is a strange thing, the nic's dont give the ability to set to 1gig, it offers me 10 full and duplex, 100 full and duplex but not 1000? Ill have a look at the switch, Id be suprised if i cant set to gig, let me check
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by:rindi
ID: 13751293
Are you sure the nics are 1gig nics? Or maybe you aren't using the correct drivers?
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Author Comment

by:credmood
ID: 13751304
Defo, they are broadcom netextreme and ive installed the latest drivers ....
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Assisted Solution

by:rindi
rindi earned 400 total points
ID: 13751347
Is the NIC integrated or an addon card? If it is integrated check the link's answer 2, point 3...

http://www.broadcom.com/drivers/faq_drivers.php#2

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by:rindi
ID: 13751511
Answer 90 of the above link on the other hand states that in order to use 1gig speed it must be autonegotiated...
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by:andyalder
ID: 13754493
Compaq (well HP nowadays) use Broadcom and let you set the speed of the NIC to gigabit, not in the Windows networking API of course but under their own utility. Procurve switches scare me, I tend to run away from them gibbering 'duplex mismatch' to myself.

I like the sound of a NAS box that is rated at 100MB/s but I would like to know what that rating means outside of being a marketing term for something with a gigabit interface and a bit of cache.

Not sure if this NAS box is also the backup server or not but it doesn't really matter, you don't have the disk hardware to hit a network bottlekneck using 100Mb Ethernet let alone gigabit.
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Author Comment

by:credmood
ID: 13759722
The drives i have in the NAS box state a Data Transfer Rate: of 100 MBps .....
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by:andyalder
ID: 13760107
That sounds like ATA100 drives which have a burst transfer rate of 100MBps across the bus. Data can be transferred from the controller to the on-die cache at that speed where it queues up to be written to the platter at a far slower rate. They probably give about 80 I/O per second random I/O which assuming 4K blocks is only 320KBps per disk. Your I/O won't be completely random of course and your block size may be bigger so you are more likely to get ten times the worst-case scenario but that's still only 3MBps. You are streaming lots of data so the RAID controller in the NAS uses its own cache to improve the RAID5 algorithm to give parallel write performance so multiply the 3MB by (N-1) disks = 9MB/s for the array.

Manufacturers love to quote the bus speed since it is fast but it is the seek rate and the RPM that dominate the performance. For example, if you replaced the U160 SCSI with U320 disks that have the same physical parameters you would improve performance by about 1%, not 100%. I have the same problem with our sales people, they tell the customer that backup to disk is faster and then after implementing it I have to explain why it isn't, it is restore time that is quicker with disks since you don't have to spool through half the tape to get to the data to be restored.
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Author Comment

by:credmood
ID: 13792568
thanks andyalder, i see your point. I assume SATA would be a bit quicker, however my NAS box is a *give away* from a company acquisition, so im making the best of what ive been given....I got a 571 MB/Min throughput on a robocopy excercise using a gig worth of data, all different file sizes, i was using the gig adapters with CAT6 cable, through a gig switch. Im thinking thats as good as it gets, still, thats not bad. If i manage to persuade them to get a further NAS box then Ill get them to get a SCSI based box, or at least a SATA one

Can i just ask, the premise of my idea, i.e over disk to a NAS box and then backing up the NAS box...is it a decent idea?  is there better ways to do this?
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Accepted Solution

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andyalder earned 800 total points
ID: 13800428
The problem of using NAS attached to thebackup server via a share is that the backup server has to read from the client through the network and then write to NAS over the network so giving a double network load. It's better to have disk-to-disk-to-tape (D2D2T) using disks locally attached to the backup server but if you have the kit available you might as well use it and it will improve restore time. I would use it for whatever part of your data you often have to do individual file restores for - exchange mailboxes for example if the users keep accidentally deleting email.

The more common use of NAS in backup is as an intermediate backup stage. Take MS SQL server, ithas its own in-built backup program and people often set this to backup to NAS through a SQL maintenance routine, easily configured through SQL enterprise  manager, then they back the NAS box up periodically with their regular backup program. That has a performance advantage over using SQL backup to the SQL servers disk and then to the backup server by getting the data off the SQL server's disks as soon as possible, the second backup of the SQL backup file doesn't interfere with the SQL box as it's already on the NAS box. Saves buying a SQL backup agent as well.
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Author Comment

by:credmood
ID: 13804140
Thats what hardware I have, I want to back up to disk to disk , then to tape, I have an SDLT600 drive attached to the NAS box via a SCSI card. The main reason i want to do this is so I can have one tape drive, at present I have about 6 DLT VS80's, the only way, I can see, to get this down, is to backup all the servers to disk and then backup the NAS box to tape.

I think that what Im doing (thanks for your help) is the best way to go about things...as you say an intermediate *store* is the most common use and thats what Im using...

The only problem I have is the IDE ATA bottleneck, however as long as I get *about* 550MB/MIN then I can live with that...

Thanks for all your advice :o)
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by:rindi
ID: 13804169
Thanks too.
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