Slow Transfer Speeds with HDD replacement

[phosphato]

Hello

I have a DS409 + NAS, and I've been happy with this for the last 3 years.

Recently one of my HDD has been broken. The units where 4 discs WD20EARS. I replaced the failed unit with a WD20EARX with the same size.

I repaired the unit without any problems although the process has taken about 24 hours.

The fact is that from that moment, I noticed the NAS very VERY slow, the NAS is only capable of read speeds above 9-10MBs and before the hard drive broke was capable of speeds around 80-90MBs.

The unit was established with SHR (RAID-5) and has the latest firmware DSM 4.0-2228, all my LAN is GIGABIT with jumbo frames 9k.

Can anyone help me please?

Thanks in advance.