Test Speed

Test Speed measures what a disk gets from its server, through your network, in about a minute. It reads and writes test files on the disk the way apps do, so its numbers are what your apps can get. Use it to see what a change on the server or the network makes.

Run it

1. In BeamDisk’s window, select a connected disk and choose Test Speed… from its Options menu.
2. The first time you test a disk, the sheet says To test it, allow BeamDisk to use the disk’s volume once. Click Allow Access… and select the volume in the panel that opens.
3. Click Start Test. Results fill in as each test finishes; Stop ends the run early.
4. When it’s done, click Done, or Run Again.

The tests

Test	How it runs
Sequential write	1 MiB, 8 at once
Sequential read	1 MiB, 8 at once
Random write, 16 KiB	32 at once
Random write, 4 KiB	32 at once
Random read, 16 KiB	32 at once
Random read, 4 KiB	32 at once
Read latency, 4 KiB	one at a time
Synced writes, 4 KiB	one at a time, each flushed: each write is safely stored before the next

Each result shows its average (MB/s, IOPS, or for latency the median), with the slowest and the fastest second of the test under it where that applies, and the Latency (median / 99 %) of each operation beside it. A test that was skipped shows a dash, and one that failed says Failed; hover over either for why.

Under the table, the sheet says when the run finished and, when BeamDisk can tell, how fast your Mac’s link to the server is (and so the most it can carry).

What it does to your disk

• Every test uses test files on the disk’s volume: a tenth of its free space, at most 2 GiB. The write tests fill them and the read tests read them back, so your own files are never touched. They’re removed afterwards, and their space is given back to the server. If BeamDisk quits during a test, it removes them the next time it starts.
• Reads come from the server, not from your Mac. The server may answer some of them from its own memory, since the test files were just written; the sheet points that out.
• A snapshot taken on the server during the test keeps the test data until the snapshot expires. The sheet reminds you.

When the test can’t run

The sheet says why, before you start:

• the disk isn’t attached;
• the disk has no volume mounted;
• its volume holds Time Machine backups, where macOS lets no app write test files;
• its volume has too little free space for the test files;
• you haven’t allowed access to its volume yet (Allow Access…).

Numbers to compare or publish

• Use a wired connection, and jumbo frames if your whole network supports them.
• Keep the Mac and the server quiet: no big builds, backups or copies running. Screen Sharing in High Performance mode slows other transfers; use Standard mode, or disconnect.
• Expect a second run to read faster: the server keeps recently read data in memory.
• If random writes come out low on a disk you formatted elsewhere, the sheet may say so: a disk formatted by BeamDisk (Erase and Reformat…) doesn’t have that problem.

What affects the numbers: Get the most from your network.