How much SSD space is enough and how much do you need?

Its enough to make a gamer cry when they look at the high prices of hard drives these days. Storing all your games and media has become a massively expensive exercise today, costing us just over double what we were paying back midway through 2010 – back then, it wasn’t uncommon to see someone fondling a 1TB hard drive with a R700 price tag on it. 500GB drives were around R450 and it was a magical time for those who bought two or more drives for a RAID array. These days you’d be lucky to even find a 2TB drive for a reasonable amount of money, let alone consider the cost of a new drive in a rig today.

So a lot of people have begun looking at SSDs because they’re roughly the same price as hard drives. You get a fraction of the drive space you would have received normally but your speed jumps up by a factor of 10 or more, boosting everything from boot time to game level loads. Its been over two years since the first SSDs filled in much-needed market space, but we’re still stuck with certain sizes. So if you’ve got the time and money to look at a drive, where would the various available sizes fit in?

The first thing to consider is how you actually use your computer. For one, there’s a size difference in the bit-versions of Windows 7. If you’re running 32-bit Windows XP/Vista/7, you’ll need at least 15GB of free drive space to fit in the OS and a few critical applications that you’d be using daily, including things like VLC, Google Chrome, Office/OpenOffice, Steam and various other small apps that could be fitted into there. For a 64-bit install, that figure jumps up to 25GB and that’s forgoing the little tweaks like re-sizing the pagefile and disabling things like hibernation that could give you back precious drive space. That’s the basic of basic installs, akin to what you’d get if you bought a new computer from a shop and they set it up for you. When I was building up certain rigs with Windows 7 for important customers, I purposely figured out ways to stay below the 30GB line for the initial install in order to keep ISO images that I could make of the drive to a minimum. If you’re in an enterprise environment, hard drive images are your best friend during a large-scale deployment, assuming all the hardware is roughly the same and you’re using volume license software.

Moving on from there, a few specific applications need to be kept in mind when choosing your SSD. Games these days chew up a minimum of 10GB thanks to the fact that very little data is read off the DVD discs after you install the game. Certain applications like Photoshop and CAD generate massive filesizes, with CAD able to generate 100MB projects just for smaller designs. High-quality bitmap images used for large-scale printing can easily measure 150MB in size as well, so things like this must be kept in mind. For the most part, if you’re using your computer for gaming or office work, its a good idea to keep the really big stuff on a second, larger mechanical hard drive. So with that in mind, where would certain drive sizes fit in for you and how would one work around the limitations?

BOOT AND CACHE: 30GB to 60GB up to R900

Starting from 30GB, you’d ideally be booting just the OS or using it as a cache drive to get that speed-up to keep things snappy. As a boot drive you’re especially limited to just the OS, drivers and a few small but critical apps. You still have to accommodate space for driver and software updates and you’d have to be especially vigilant with keeping your media on a separate drive. As a cache drive, though, both sizes are perfect. If you’re already rocking a Windows Vista or 7 install and have a motherboard that supports Intel’s Rapid Start Technology (RST), you can simply pop on the SSD and configure it as a cache drive in the BIOS. The drive will then cache frequently-used data, speeding things up in the same way. The only caveats are that, occasionally, your cached data will get overwritten if there’s a lack of space for new data, hence why I’d recommend a 60GB drive for caching. The other one is that while data writes are done to the SSD first and then to your regular hard drive, those later writes are often slow and if done during a power outage, will introduce some data corruption and system irregularity. Cache SSD drives are limited to 64GB in size, with the possibility of Intel lifting that limit to 128GB sometime later this year.

Drives I’d consider in this segment: Corsair Nova 2 30GBOCZ Petrol 64GB, OCZ Agility 3 60GB, Transcend SSD720 64GB, OCZ Vertex 3 60GB and the OCZ Agility 4 and Vertex 4 60GB drives (both hugely impressive thanks to Indilinx controllers).

BOOT, APPS AND GAMES: 90GB TO 128GB up to R1800

If you’ve got a little spending money extra, its worth your while to explore the larger drive sizes. 90GB is where I’d consider loading on the OS, all your apps and one or two games onto the SSD, with the remainder of your media on a larger drive. If you’re setting up an office computer, 90GB is also a good starting point and won’t need a second drive if all you’re doing is word processing, e-mails, internet, document creation and using database-reliant programs like Pastel. 128GB is even more capable, fitting up to four extra game installs to boot. Its worth considering that a database-reliant program like Pastel behaves a little differently on a SSD. Pastel and Pervasive Workgroup or Client-Server in particular makes about 4-5 writes to the database for a single action, occasionally replicating the action elsewhere in the company files or adjusting stock levels and other things like average price records while doing batch operations. These writes are normally transmitted over the network to the Pastel server. Occasionally this stuff queues up and forms a long line if big transactions and sales are taking place all at the same time.

Since SSDs have a near-zero access time, it makes a lot of sense for a Pastel server to have one installed. Because a lot of the network usage is spent on replicating the changes to the database from within the client application to the server (especially in Pervasive Workgroup), a slow hard drive clogs up communications while the user waits for data to be written and a result returned. On a busy sales day, one of the servers I was taking care of at a previous job would just simply freeze up after too many network accesses, prompting me to shove in 10,000rpm drives and two network cards to solve the access time problem when multiple people were working on it. A SSD would have solved that issue and would have been doubly or even triply faster. So if the majority of your work is mission-critical and needs to be done quickly in software, SSDs help chop the time taken to do a certain thing like loading up Photoshop or Adobe Illustrator by nearly three quarters of the regular time.

Drives I’d consider in this segment: OCZ Agility 3 120GB, Corsair Force3 90GB and 120GB,  OCZ Vertex 3 and Vertex 4 120GB, Transcend SSD720 128GB, Intel 330 120GB, ADATA SP900 and SX900 128GB

BOOT, APPS, GAMES AND MEDIA:  180GB TO 256GB and beyond

Ideally, this is where your investment pays off for itself. At this level there’s no real need to worry about how much space you’re using because you have quite enough for games and apps already. Starting from the 180GB mark this is where you’d only house large media files on another drive, but keeping your user folder on the SSD no longer brings any space deficit in terms of percentage or the drive used. At this level performance hits the maximum the drive controllers can handle, as we’re now filling up all the available bank space and that has speed benefits as more cells are accessed in tandem. Drives at this level are also the same size as those commonly found in boutique PC builds and Ultrabooks, being the verge of where speed meets acceptable storage size for a rather good price.

The metric to measure value here, as for the other, smaller drive sizes, is the R10 per GB mark. If you’re scoring a 90GB SSD for R900 or less, you’re falling under that line and the drive is a bargain. Anything over that R10/GB mark and things muddle themselves up very quickly, with “performance” SSDs, like Plextor’s Toggle-mode NAND drives,  confusing things even further. I wouldn’t recommend spending anything more on a drive larger than 256GB because that’s the limit of the value-for money segment, at which point it becomes more expensive per GB to buy the damn thing.

Drives I’d consider in this segment: OCZ Agility 3 and Agility 4 240GB, Transcend SSD720 256GB, ADATA SP900 and SX900 256GB, Corsair Force3 240GB


The holy grail of hard drives, RAID arrays allow for huge storage volumes in desktop computers and servers and even yours truly is looking to invest in a three 2TB drives for a 5TB RAID 5 array in the future. SSDs have, up until now, run into a slight wall with regards to RAID and TRIM support. TRIM is the software solution to keeping the performance of your SSD in top shape, erasing information in 4KB data blocks to clean up the NAND cells properly. Without TRIM, free space on the drive drops over time and performance suffers as more cells remain populated with unused data that has been “deleted” by the OS.

The workaround to this software solution is a built-in hardware option that even runs in RAID, called Background Garbage Collection (BGC). What it does is recognise which cells are half-filled or half-erased during idle time or when the drive isn’t being fully utilised and cleans up those cells by putting the data from half-full cells together, freeing up other cells for use – that’s defragmentation in a nutshell, really. The benefits of this is that BGC allows extra data onto the drive even while it’s doing its job and it keeps performance at the same level as TRIM even after a year of use in a RAID array. The only drawback, near as I can see, is reducing the drive life thanks to the extra reads and write that BGC necessitates, while TRIM only keeps track of the status of cells and doesn’t do it as frequently.

However, there is hope for TRIM in RAID. Intel’s new RST drivers have added in TRIM for RAID support, but it has been slightly buggy for some since its inclusion in the RST driver in November 2011. Today TRIM for RAID is included by default and is very stable, covering scenarios from a RAID 0 and 1 array to RAID 10 (a mirrored array consisting of striped drives). RAID 5 isn’t catered for, owing to the huge degradation in performance it would encounter thanks the error correction mechanisms that RAID 5 needs to cover the single drive failure scenario. The error correction is so busy in RAID 5 that it would easily reduce drive life from the regularly expected five years right down to less than three in an active array, thus it hasn’t been implemented. If you have enough cash to spend on a 512GB drive, its worth the risk to rather put two 256GB drives in RAID 0, just about doubling performance and drive life in the process.

Source: Anandtech, Tom’s Hardware

Further reading: Sean’s SSD and HDD Windows 7 Optimisation Guide

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