hello, the topic is very old, but i hope someone still reads it. I was also very confused with this whole sata sas interposer thing. First i read on some forum that interposer can make sata look like sas to the system, therefore allowing SAS + SATA in RAID1 on the same virtual drive. WRONG!!! there is no way that could ever work. Then i read that the interposers are mandatory for the SATA drives to work on perc5i controler. WRONG again!!! SATA drives work with 2 different caddys without any interposer. So... interposers are no use for poweredge 2900 - 2950 what so ever! they are a waste of time. the only thing is... SATA are like 20x times slower then SAS drives.
Config: dell poweredge 2950 6 hdd bays
hdds: 2 seagate 1TB sas 7200k rpm vs. 2 seagate 1TB sata 7200k rpms
after setting them up in raid config utility at boot, the 4 hdds began mirroring.
SAS drives - 24% done
SATA - 4% done
Am i doing something wrong? or the sata drives are that slow... ?
Not only do SAS drive typically have a higher RPM (10K/15K vs typical SATA 7.2K), but SAS has many other features that make them faster than SATA (full duplex, caching, performance settings, etc.):
thank you for your quick reply. but in my case the rpm are the same, so that leaves the other feathures that the sas has extra. how reliable are SATA on a hosting server ? talking about speed and functionality... ??
If you look at the matrix on the Intel doc, many of the features affect reliability too ... error recovery and other SAS settings that SATA drives do not have. Another thing that addresses reliability is Dell's warranty ... SATA drives, unless you purchase an extended warranty to cover SATA, is only 1 year, where the SAS drives are covered for the term of the server's warranty, up to 5 years.