Urbackup limitations

Is there any limitation on the amount of clients a server can handle? I have a site with 500+ clients and there is only growth happening going forward.


There aren’t any limitations on how many clients it can handle. It will use a lot of RAM + you need RAM for database and file system cache, so the starting point is at least 32GB RAM here (with a lot of clients).

If one server can handle 500 clients depends on how often you want to back them up, how many files they have and how often those files change. At some point you’ll probably have to scale it out horizontally.

If you put the UrBackup database on a SSD (which is a must) the performance will likely be limited by backup storage random IO, so keep that in mind when choosing between e.g. RAID10 and RAID60.

What server OS are you planning to use?

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Uroni , thanks for the follow ups. I plan on using Centos 7.

Hello Team,

We are planning for a backup solution for 500 windows clients.

Windows Server 2016 with 32 GB Ram 4 Core processor & NAS with ISCSI 30 TB 7200 RPM SATA drive. Please guide us can we proceed with this hardware configuration.

Since none of the larger network users have replied, I’ll drop a few hints from my experience with several offices of around 20 clients each.

I use Server and Client to to distinguish the UrBackup Server and Client software from the computers running the UrBackup programs. One may run the Client on a “server” computer to back it up or the Server on a small client-type computer if your needs are modest. The words server and client without capital letters generally refer to the computers running that part of UrBackup unless otherwise indicated by context.

First a comment on size. UrBackup uses network broadcast messages to communicate with local clients. This is done continuously to see if a Client is online, not just when adding a new client computer. On IPv4 this means a maximum of 254 clients can reside in a single subnet. Since broadcast messages do not cross subnet boundaries, you may need to add half your clients manually, either as Internet Clients or by using the DNS hostname or IP address so the Server can locate the new Client.

Do you plan to create image backups of the clients for quick recovery after a drive failure or malware infection? A typical system I see uses about 80 GB for Windows (C: drive). After UrBackup skips the pagefile and hiberfil and a few other unnecessary items, that’s about 65 GB to back up. If that applies to your 500 clients, that’s 33 TB to save a single full image backup of each client. You’ll want at least two full and a few incremental backups for safety, so 80-100 TB just for images, unless you have a different way to deploy a replacement client.

Another consideration is network bandwidth. I just kicked off a full backup of four clients at the same time on a 1000 Mbit network. UrBackup shows a transfer rate of around 120-130 Mbits for each client, and estimates the backup will take 50-60 minutes for all four to complete. (One actually took 74 minutes.) If I had 500 clients on the same network, it would take 125 hours or 5.2 days of continuous backups to get all the clients protected with one image. Let’s assume a 14-hour overnight backup window. Your backup server and network could be tied up for 10 consecutive days during the overnight maintenance time when other large network tasks generally run. You’ll want a faster backbone and at least a 10 GB network link from the main switch to the server or risk serious degradation of network performance during times of multiple image backups. This can be managed but it requires extra thought.

Of course full image backups are the worst-case for performance. Good block-level storage deduplication (available in later versions of Windows Server) can help a lot, especially if all clients have a very similar Windows image. In that case you’ll want to turn off UrBackup compression so Windows can see the raw image files.

I used to have the typical example of C:\Users in my settings, but that pulls in a ton of temporary cache files from web browsers, antivirus applications, and printing from the AppData folders. Now I select only the documents and picture folders where user-created files are saved, and backups take a lot less time and storage, and don’t generate so many errors when the file is changed while the backup is running. Be aggressive in using the included and excluded files entries in the settings. It makes a big difference!

If you use image backups and do incremental images every few days, this will catch most files that may have been skipped by your include/exclude settings. There is a risk that recent work will be lost before the image backup occurs, but recent work may be redone easier than older files where nobody remembers exactly what was in them. Try for perfection but keep several alternative ways of doing things in the back of your mind, just in case.

I think you’ll want more storage and a fast network connection to your backup server. Be sure you have an SSD (either SATA or NVMe) for UrBackup to use for its temporary files - they get a lot of read/write access during backups. An SSD for the C drive will also help, as UrBackup keeps the database files in C:\Program Files\UrBackupServer\urbackup. If necessary, use several backup servers and assign the clients based on their subnetwork to divide the workload. You’ll lose a little on deduplication, but gain performance by spreading the network traffic around.


Awesome response, @Don_Wright

Technically, if the network in question were a /23 instead of a /24, all 500 machines could be in the same broadcast domain, but that would just transfer the problems to another part of the infrastructure.

@Don_Wright provided some awesome advise.

To answer your question effectively, you need to tell us what kind of backups (image vs file; full vs incremental) you plan to perform and at what intervals, and how many copies you plan to keep.

What’s the average size of the client data to be backed up?

You definitely want to be able to split those backups up over a number of backup servers, unless you’re just interested in saving ~ 30GB of data per machine, max (which would be 14.6 TB before deduplication).

Also, I just noticed that this would be iSCSI. What’s the bandwidth between the server and the iSCSI storage? Hopefully, more then 1Gbps.

Do the math that @Don_Wright recommended, and then use that to figure out how many servers and what kind of bandwidth is needed.