Server SSDs usually come in three endurance classes: read intensive, mixed use and write intensive. The label tells you how much data a drive can take before it wears out. Pick too low and the drive fails early. Pick too high and you pay for endurance you never use.

That second mistake costs more this year. TrendForce expects NAND contract prices to rise 15% to 20% in the fourth quarter of 2026. Enterprise SSDs are the one memory type where price rises are getting bigger, not smaller. Hard drives face a similar squeeze, as our server hard drive shortage guide explains.

Quick answer: Many servers do well with read intensive SSDs. They sit at about 1 DWPD or less. Choose mixed use (about 3 DWPD) when reads and writes both run steady. Choose write intensive (about 10 DWPD on Dell drives) only when writes dominate. Measure your daily writes first, then pick the class that leaves room to spare.

What is DWPD?

DWPD stands for drive writes per day. It counts how many times you can fill the whole drive with new data each day. The rating runs for a set number of years, and Dell and HPE both use five.

Here's the math. A 960 GB drive rated at 1 DWPD can take 960 GB of writes a day. Over five years, that adds up to 1,752 TB (0.96 TB x 365 days x 5 years). That total is the TBW rating, short for terabytes written. The formula is DWPD x capacity x 365 x years. Kingston walks through it with its own examples.

Two more points. First, the years matter. A shorter rating period means a lower TBW at the same DWPD. Second, both companies rate drives on small random writes. HPE uses 100% random 4 KiB writes. Dell's brief calls its test a worst-case 4K random workload. That's a hard test, so your drives may do better. Still, plan around the number.

Read intensive vs mixed use SSD vs write intensive SSD: the quick comparison

Dell's brief for its PX05 SAS SSDs lists all three classes side by side. The DWPD and TBW figures below come from it. The last column is general guidance.

Read intensive is the everyday choice. It suits jobs that read far more than they write. HPE lists read caching, web servers, social media and boot as read-driven work. Kingston notes that higher DWPD often carries a price premium. So read intensive is usually the easier fit for a budget. An HPE read intensive SSD is built for this kind of work.

Mixed use sits in the middle at about 3 DWPD. HPE's drive selector points to it for balanced read and write needs. The read intensive vs mixed use SSD choice comes down to the write budget. At the same size, mixed use gives you at least three times as much. Virtual machines, file servers and general databases often land here. A Dell mixed use SSD is the step up when a read intensive drive runs short.

Write intensive is for heavy jobs. Dell rates its PX05 write intensive models at 10 DWPD. Think logging, write caches and busy databases. Most servers don't need that much, and the extra cost goes to waste. A Dell write intensive SSD makes sense when your measured writes call for it.

How Dell and HPE name these classes

Dell uses all three names, so a Dell write intensive SSD is easy to spot. HPE's SSD QuickSpecs also has three classes. They are very read optimized, read intensive and mixed use. HPE's drive selector points the first one at very read-heavy work such as real-time analytics. The list doesn't include a write intensive class. For heavy writes on a ProLiant, start with mixed use. Then check the DWPD printed for each model.

The class name isn't one fixed number, either. Look at any HPE read intensive SSD on that list. Most SATA models list 0.8 DWPD, or 0.7 on the 7.68 TB size. Its SAS models list 1. HPE's SATA mixed use drives sit at 3. One self-encrypting mixed use model lists 5. The same labels also appear on NVMe drives. So read the DWPD, not just the label.

Capacity matters as much as class

Class sets the DWPD. Capacity sets how much writing that adds up to. Dell's brief shows it. Dell rates a 3.84 TB read intensive drive for 7,008 TB written. It rates a 480 GB mixed use drive for 2,628 TB. The "lower" class takes about 2.7 times the writes, since the drive is eight times bigger.

Now flip it. Say one drive takes 2 TB of writes a day. On a 480 GB drive, that's about 4.2 drive writes per day. That's more than mixed use allows. On a 3.84 TB drive, it's about 0.5, well inside read intensive. So before you move up a class, check whether a larger drive solves the problem.

How to work out the DWPD you need

1. Measure your writes. Dell's Live Optics is a free, vendor-neutral tool. Its Average Daily Writes figure is the one you want, and Dell's guide explains it.
2. Add the RAID cost. RAID writes extra data. Dell's guide uses a penalty of 2 for RAID 10 and RAID 5. For RAID 6 it uses 3. Multiply your daily writes by that number.
3. Divide by raw capacity. Divide the result by the combined size of the drives in the set. The answer is the DWPD you need.
4. Leave room. Double your number as a safety margin. Then pick the first class at or above it. That's 1 DWPD for read intensive, 3 for mixed use and 10 for write intensive.

Here's an example. A RAID 10 set of four 1.92 TB drives takes 1 TB of writes a day. RAID 10 doubles that to 2 TB. The set holds 7.68 TB of flash, so the need is about 0.26 DWPD. Double that and you get about 0.5. A 1 DWPD read intensive drive covers it with room to spare. Dell calls its own method a worst-case estimate, so real wear should come in lower.

How to check wear on drives you already run

Your server already tracks it.

• Dell: iDRAC shows Remaining Rated Write Endurance for each SSD on the physical disk page.
• HPE: Smart Storage Administrator lists SSD wear status, usage remaining and estimated life remaining.
• Linux with NVMe: Run smartctl -A /dev/nvme0n1 and read Percentage Used. It's the vendor's estimate of life used, and it can pass 100%.

Heavy wear early in a drive's life tells you the class or size was too small. Almost no wear after years tells you that you can step down next time. If you're weighing pre-owned SSDs, ask the seller for the wear report and power-on hours.

Read intensive vs mixed use vs write intensive SSD FAQ

What is DWPD on an SSD?

DWPD means drive writes per day. One DWPD lets you write the full drive once every day. Dell and HPE both rate drives over five years.

What is a good DWPD for a server SSD?

For many servers, 1 DWPD or less is plenty. Kingston cites Forward Insights data. In it, 82.3% of data centers and enterprises on SATA drives do well below 1 DWPD. Heavy write jobs may need 3 or more. Measure first.

Is TBW the same as DWPD?

They measure the same thing two ways. DWPD counts full-drive writes per day. TBW counts total terabytes over the rating period. Multiply DWPD by capacity, 365, and the years to get TBW.

What happens when an SSD reaches its TBW?

The drive doesn't die that day. Lenovo's drive guide says hitting the limit doesn't make a drive fail right away. But the guarantee ends there. Plan the swap before you get close.

Can I use a read intensive SSD for virtual machines or databases?

Sometimes. HPE says business intelligence, big data analytics, and virtualization tend to be more write driven. If your measured writes stay well under the drive's DWPD, a read intensive drive works. If not, move to mixed use.

Can I replace a Dell mixed use SSD with a read intensive one?

Only if the math says it can take your writes. A larger read intensive drive can out-last a small mixed use one, as the capacity example shows. Match the interface (SAS or SATA), the form factor, and the tray. Check your controller guide before you mix classes in one array. The lowest-endurance drive usually wears out first. If you're swapping a failed drive, our hot-swap replacement guide covers the steps.

Pick by the numbers, not the label

Measure your writes, read the DWPD on the data sheet, and leave some room. That beats paying for the top class by habit. We carry new and pre-owned storage hardware, including Dell and HPE enterprise SSDs. If you're unsure which class fits, contact CPU Republic with your server model and daily write numbers. Our part number guide can also help you read the label on the drive you have now.