16x 600GB 10K SAS in raid question

[dude05]

I finally got myself a fractal design define XL and 4x icydock bays for sas drives and 16x 2.5"m 600K seagate drives. another 15 more drives on the way. I am planning to have 16x sas on my areca 1882ix-16 and stripe 15 of em on raid5 inside centOS7.2 for use with flame.

Will it be ok? I have heard clashing info that raid 5 only works best for 8 drives max and anything more will throw the performance away. Will there be anything I need to keep in mind? I am hoping for a 2000MB/sec rw speed. anything that would stop me from getting it in your understanding of drives/raid/OS ??


thanks in advance

 

[i386]

Parity raid (5/6/proprietary 7) gets better read speads with more drives, write speed stays the same (=speed of 1 drive).(Caching on the raid controller helps a lot with improving write speed though).
2 gbyte/s read: possible
2 gbyte/s write: no, not with raid 5

From my view: I would always use hdd parity raid for capacity and raid 10/mirrors with ssds for performance. If performance AND capacity is a requirement look at raid controllers with ssd caching support.

 

[dude05]

write speed stays the same (=speed of 1 drive)./QUOTE]


thanks

Curious why u say the write speed will be the speed of 1 drive?? I got few raid5s in my shop. 1 is 11x4tb enterprise with 1 hotspare giving me abt 1200MB/sec on read and write for 4Gb files. i never went past the 11drive setup so i was wondering if it would affect speed. but i do get speed of 10 drives in any given situation unless the storage is more than 90% full.

is there something i am not thinking here? or unaware of?

 

[i386]

Curious why u say the write speed will be the speed of 1 drive??

The parity write penalty. Without caching you have to read data, read parity, write data, calculate new parity, write the new parity.

My guess is that you are writing to the controllers cache with the 4gb files and not directly to the hdds.