Two important questions about the sitemap

1. How big should the sitemap be? I have a problem with my forum host because they have a security limit of 1MB. If the sitemap is bigger than this, is is blocked.

2. Why do I have two sitemaps?

Hello,

1. that is rather strange limitation You can set the number of URLs per file in generator settings to "5000".
2. sitemap_index contains a *list* of sitemap files only (in your case just one file), while sitemap_1,2 etc contain URLs.

So having these two sitemaps is normal then? And what is the normal size of a sitemap?

Yes, this is normal. Default setting is 20000 URLs per file.

20000 URLs = 2MB?

The file size depends on the length of URLs (which varies of course), but as long as you have gzip compression supported it should be much smaller than 2M, may be about 200-300K. The simplest way is to create sitemap and check the actual file size in vbseo_sitemap/data/ folder. via FTP

Thanks Oleg! Where do I enable gzip compression?

It is enabled by default.

Sitemap File #1 sitemap_1.xml.gz (19,042 URLs, 3,516.78Kb) 3,516.45Kb uncompressed
It does not seem compressed...

It shows the uncompressed size in reports, but the file itself is compressed. Your sitemap_1.xml.gz is about 200K in size, there are no issues with it, and as it's seen on screenshot from the first post, it was accepted by Google.

Thanks!