PowerEdge HDD/SCSI/RAID

[evilbug]

We've just received a PowerEdge 2950 with PERC 5/i controller. We've ordered a single SATA drive since we'd like to put in 6 of our own.

My understanding is that SATA drives must be connected to PERC 5 backplane with an interposer board (part #PN939). This was also confirmed by a DELL tech on the phone.

What I am confused about is that DELL's SATA came installed without an interposer board. Looking into the drive bays, I can see markings such as "J_SASDRV0" and so on through 5. I've replaced DELL's drive with my own SATA drive and it was recognized and seems to function fine without the interposer. So is the interposer board needed at all then? I need to order additional HDD trays and now I am not sure if I have to order interposer boards for each drive. Maybe I am not getting it right and any advice is appreciated. Thanks!

[evilbug]

From a bit more digging, it looks like the interposer is just a kind of an adapter to allow use of SATA drives in trays that fit SAS drives only. All I need to get are SATA trays. Just need to find the correct part numbers then. If anyone dealt with this before, then I'd appreciate a part number for SATA HDD tray for PowerEdge 2950.

Message Edited by evilbug on 05-04-2007 02:59 PM

[evilbug]

Hopefully I am the only one who was confused, but in case there are others, here is what I was able to find.

The HDD caddy that DELL told me (and probably others) to buy for SATA drives is part number CC852. This tray, I was finally told, is longer (I guess different hole placement?), so it requires the interposer board to simply extend the HDD so it'd reach the backplane. Interposer board doesn't have any advantage or disadvantage over connecting SATA drive directly to the backplane.

The caddy part number that I purchased is F9541. It does not require the interposer board and lets a SATA drive connect directly to the backplane.

[cjtompsett]

The SATA interposer board is needed when using the drive in the MD1000 enclosure.

-cjtompsett

[tommo666]

SAS drives and SATA drives use the same style connectors. THe data and power connectors are the same. The differevnce being the format of the drives. The connectors are posititioned slighly differently.

The caddy supplied for 3.5in drives can support both drives. There are different (marked) screw positions for each flavour of drive.

[tbleier]

Hi,

I have a PowerEdge 2900 which I suppose uses the same backplane as the 2950. I ordered it with 2 SATA drives (250GB). The are in a a caddy that is marked with "SATA + SAS" and they have the "interposer" board.

Then I ordered a 80 GB SATA drive, since it seems the cheapest way to get the caddy here (EUR 45,- for drive + caddy). It came only with the harddisk (no interposer), and was marked with "SATA" only. The screw holes were obviously at different positions, so that the bare drive still connects to the backplane.

Both solutions work, so I see no difference.

Just my 2c,
__
/homas

BTW: where can one get that caddies - cheaper than EUR 45,- (around $60) - in Europe?

Message Edited by tbleier on 05-21-2007 12:42 PM

[alex_sabau]

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... ?

[theflash1932]

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.):

www.intel.com/.../CS-031831.htm

blog.whitesites.com/SAS-RAID-0-VS-SCSI-RAID-0-VS-SATA-Benchmarks__633689244191943184_blog.htm

ftp://ftp.compaq.com/pub/products/servers/proliantstorage/drives-enclosures/sata-vs-sas.pdf

[alex_sabau]

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... ??

[theflash1932]

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.