CIFS sequential reads slow, writes fast. How to improve..
We have an Intel SSR212MC2 Storage Server. We use the NAS functionality of the DSS to provide CIFS shares to Windows server for the storage of backup images. (Images are created using Backup Exec System Recovery).
Every week we need to perform a full backup of our DSS to tapes in our Tape Library controlled by Bakbone NetVault. Because Open-E does not support the NetVault backup agent, nor does it support NDMP on NetVault we are forced to backup the DSS using a CIFS share. The problem is the maximum speed we can get is around 30-35MB/sec. However we can write to the DSS using CIFS at 101MB/sec constant (maxing GB network link). We have spend many many days if not weeks trying all kinds of raid settings, different clients (linux, windows, etc), non of which has made any significant difference.
We also have an older SSR212CC which suffers from the same issue. We concluded however that this issue is related to the CIFS protocol, and not to any disk or network bottle necks. The reason for this is if we transfer using FTP we can both read and write at 100MB+/sec constant. Also if we install standard Linux distro on this hardware and then install NetVault backup agent, the NetVault server can transfer from the agent to the tape library at 80MB/sec (max speed of LTO3 tape drive). So clearly this is a CIFS protocol / tuning issue.
So my question is why are CIFS reads 3 times slower than writes (one would expect writes to be slower)? I would also like to hear from other people about what kind of sequential speeds they are getting from CIFS shares. Open-E, the SSR212MC2 is certified by you - surely you have some performance metrics available for this system? What, if any, CIFS tuning options are available for the DSS (I can't find any)? How are people backing up their multi-TB filers? Please don't tell me you are using replication - replication is NOT a backup.
I would like to see better backup agent support (or the ability to install your own agent). Or at least much better support for NDMP. (providing it is faster than CIFS). Squeezing as much speed out of filers for sequential reads is critical today with such large systems. Without reliable, robust and fast backups the DSS is a useless product. :(
