Which models are you considering?

You need to download and the owner's manual.

I have the Optiplex 3020 SFF. It only has space and SATA connector for 1 hard drive.

You cant do that with USFF because of power and space limitations.

Dell Sweden now offer several of their models at very reduced prices (- 30%) AND they still have Windows 7 Professional, which I like much better than Win 10. It is a tempting offer to me, but the pictures show boxes in two very different sizes, and they don't say which of the sizes is the actual. The text don't specify the outer sizes, and nothing about the possibility of space/connections to a second hard drive. That's why I am confused of what  they actually offer. The model I am interested in is the Optiplex 7020 "small form factor" and using a SSD C:disk. In the text they write nothing about which of the two sizes the Picture shows.
Here it is:
www.dell.com/.../pd;model_id=optiplex-7020-desktop

The unit on the left is SFF.  

The unit on the right is what Dell calls mini tower. That is the one you want if you want to put in more than 1 hard drive.

The unit on the left is SFF.   The unit on the right is what Dell calls mini tower. That is the one you want if you want to put in more than 1 hard drive.

Quite false. The 7020 SFF comes with a double sided caddy to allow for 2 drives, as well as 2 power connectors. The DVD drive, if you have one, uses a different type of power connector, and there is a third SATA port on the motherboard for it.

I am interested in a purchase of a small form factor but I can't find informations on the outer sizes and if it is possible to connect and use two (HDD or SSD) disk drives inside the unit. Overall, there is very Little information of the units on Dell's web site. My idea is to purchase a unit with a SSD disk AND later complete the unit with a F:-drive of at least 2 TB. I haven't found any infos of the number of USB-connectors and if they all are USB3.0. I also would like to connect my old VGA display to it. I deal mostly with sound recordings and I have no use for better quality on the graphics. What is the smallest form factor that allows space for a second HDD?

The Optiplex 7020 SFF comes with a 2.5" double sided caddy. The power connector has a Y split to allow for 2 drives. Ideal set up is a SSD for the OS and then a large HDD for storage. See pic. As a side note, I bought a USFF Optiplex 780, (SFF: small form factor USFF: ultra small form factor) and although it doesn't come with a double sided caddy, if you get your hands on one you can absolutely put 2 2.5" drives in there, but you'll have to disconnect the DVD drive (mine didn't come with one so no problem).

ieee488 The unit on the left is SFF.   The unit on the right is what Dell calls mini tower. That is the one you want if you want to put in more than 1 hard drive. Quite false. The 7020 SFF comes with a double sided caddy to allow for 2 drives, as well as 2 power connectors. The DVD drive, if you have one, uses a different type of power connector, and there is a third SATA port on the motherboard for it.

All I know is that my 3020 SFF came with one caddy. So, 1 hard drive and 1 DVD drive. 2 SATA cables and 2 power cables.

Here's the Dell spec sheet on the 7020 http://i.dell.com/sites/doccontent/business/smb/merchandizing/en/Documents/Dell-OptiPlex-7020-Technical-Spec-Sheet-FINAL.pdf

My 3020 SFF has the 3.25" hard drive and the 5.25 slimline DVD drive. There is no splitter as in your photo.   My 3020 is 3 months old.

Thank you very much for your answer. I will buy that 7020.

Thanks!

Ingemar

The R494D caddy is for 2.5 inch drives and snaps into the 3.5 bay. This is not a guarantee that all come that way.

Not sure if I understand you, but the main issue for me is to be able to use two drives: one SSD (C:) and a second HDD (F:). I don't mind so much if it is necessary to use only a 2,5" drive for the F: as long as it is possible to connect and make room for it. I must have a CD/DVD drive in the unit, so a solution where I must disconnect the optical drive to use its connections for the F:-drive is not a solution for me.

Another issue is - because I am now using a laptop connected to an external screen, keyboard, mouse - if the DELL 7020 also has WiFi. I want to continue using WiFi as my normal internet Connection.

Also, on the Swedish web site for Dell, they offer several 7020's which in the table of specs seem to have equal performances, but they differ very much in prices. They have equal processor, RAM and 128 GB SSD, and they all have Windows 7, but very different prices. If I buy the cheapest one (5419 Sw.kronor), what will it miss compared with the most expencive one (7219 Sw.kronor)? The prices are also without the Swedish VAT tax (25%), so the difference grows when VAT is included.

Ingemar

http://en.community.dell.com/support-forums/desktop/f/3514/t/19605696 Dell claims that two 2.5" drives will fit in the 3.5" but does not give further details.  The manual for the SFF does not explain about two 2.5" drive contrary to what the Dell technician writes.

In another thread, http://en.community.dell.com/support-forums/desktop/f/3514/t/19587031  it is mentioned that you can use a 3rd party adapter for two 2.5" hard drives.

I just picked up a 7020 with 500gb hdd I wish to swap for a ssd.

I read it is normal to put the drive containing the OS on the first of the sata connectors. This presents a problem. SATA0 is 2.0 while SATA1 and SATA2 are 3.0

Obviously plugging a SSD into a SATA 2.0 position will cap it's performance. While plugging the OS containing drive into SATA1 or SATA2 positions is technically wrong.

Which is the lesser evil, and how will I suffer?

Part number for the 'Optiplex 3020 7020 9020 2.5 inch caddy' ?

The Optiplex 3020 7020 9020 R494D 2.5 inch caddy fits inside the DN8MY 3.5 inch blue caddy for the Tower.

The Desktop and SFF have different part numbers for the Internal 3.5 caddy but that does not matter because the R494D converts the 3.5 to a bracket that holds 2.5 inch drives and then snaps into the 3.5 caddy.

The Silverstone adapter has all the mount points of a standard 3.5" hard drive, and it's only $8 with free shipping. It holds two 2.5" devices stacked.