Write performance - Raid 1 or 5?




do you think that RAID 1 would be faster in writing big files than RAID

I have a NAS (Allnet 6400) that I use for backup purposes, I transfer
only big files over night. I have 4 disks with Raid5, I can write files
with approx. 45Mbit/sec which I tested with robocopy. I have another
NAS which reaches 128 Mbit/sec, so network speed would allow more than

I tested a full Backup with 128 GByte. To a SATA drive in a PC (over
100Mbit-net) it usually takes 3.5 hours (80Mbit/sec), to the Allnet NAS
it took 6.5 hours (44 Mbit/sec), so I am wondering if the RAID Level
might be the problem. Testing is hard as it will take ages to copy data
back an forth and rebuilding the RAID (min. 12hrs).



Juan Perez


That is for sure. In Raid 1 all you have is two HDDs were you transfer in
information and almost at the same in written without any delay.

In RAID 5 you have a minimun of 3 HDD, were you 1st you transfer the
information to three devices and later you hace to do some calculation, I
am talking in aRAID by hardware, or CRC in order to keep the info in a safe
way. If you were working with "small" files, you might not feel a big
diference. But ypu are talking about 128Gb files, and that is huge...


Hello Juan,

thank you for your post. I will test Raid1 now. I read some articles
about Raid but none was discussing write speed for big files comparing
Raid 1 with 5.

I thought that Raid 5 could be as fast as Raid 1 because the data may
be "split" and written "simultaneously" which would improve the
performance that is lost by writing the additional parity information.
But obviously I am wrong :)


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