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Slow write Raid 5

Guido W!tty
Occasional Contributor

Slow write Raid 5

i have some problems with write speeds.
Done a test with a 7 GB file.

copy from server 1 to server 2

with 100MB lan speed: 12 min. 50 sec
with 1000MB lan speed: 13 min. 42 sec

The free RAM in server 2 start at 1 GB and the server says it needs 5 minutes to copy.
After 6 minutes the free RAM drop to 20 MB!!! and the copy time ingrease to 15 minutes.

After the task was done, the free RAM slowly climed up to 900 MB.


2 x :
ML 350 G3
2003 server std SP II (clean install)
compaq 431 array controller
5 x 18.2 GB UW 3 SCSI in RAID 5 (4 + spare)
GB switch
newest firmware + drivers

Does enyone know how to speed thinks up?
Or do i need RAID 1 ?

In the future it is gonna be a file server, so i need some speed ;-)

Honored Contributor

Re: Slow write Raid 5

It looks like a network issue. You may have backbone/routers which are restricting you to a certain speed (because going from 100BM to 1GB doesnt seems to be gaining performance. try to ping the servers and see what's the response time. Look at nslookup from server1 to server2 and see how many devices are in the way.

Have you checked whether FULL-DUPLEX settings enabled on network card or not?

I feel that going from RAID5 to RAID1 may not help you.

My 2 cents worth.
Frequent Advisor

Re: Slow write Raid 5


I dont think its a LAN problem, your RAID just isnt fast enouth.

RAID 5 has a bad write performance because if the parity calculation.

On the other hand: 7GB in 12 minutes isnt so bad. For most of the fileservers its more than enouth.