LSFS Cache

[KLSsandman]

Hi,

When creating a new LSFS device of 8TB it says I need around 60GB RAM for caching (with no dedupe or autodefrag), and as I result of me only have 24GB spare it can only create a 6TB disk. With dedupe and defrag enabled it wants over 80GB RAM free!

Whats the ratio? I'm trying to work out how much ram our production starwind servers would need to create LSFS disks. Does it really need all that ram?

We currently have:

3 x 1.17TB datastores
3 x 2.64TB datastores

Thanks
Simon

[anton (staff)]

It's not a cache these are hash and metadata in-memory tables actual LSFS cache (sitting below dedupe engine and thus working with deduped data) is quite different thing.

LSFS needs aroung 5GB for every 1TB of served data.

We work with post-V8 with a fixed 4KB blocks (compare this with floating 32KB+ off-line MS dedupe and dynamic ZFS blocks) and need ~6 bytes for hash entry (ZFS needs 200+ bytes *OR* would increase dedupe blocks resulting not so good savings) I don't think LSFS is a real "memory pig" here

Hi,

When creating a new LSFS device of 8TB it says I need around 60GB RAM for caching (with no dedupe or autodefrag), and as I result of me only have 24GB spare it can only create a 6TB disk. With dedupe and defrag enabled it wants over 80GB RAM free!

Whats the ratio? I'm trying to work out how much ram our production starwind servers would need to create LSFS disks. Does it really need all that ram?

We currently have:

3 x 1.17TB datastores
3 x 2.64TB datastores

Thanks
Simon

[KLSsandman]

Hi Anton,

Thank you for your reply, I understand it now. Home lab will struggle to get enough ram to provide for 8TB with server grade motherboards Production will be fine though.

Thanks
Simon

[Anatoly (staff)]

Well, you can always test if that`ll work for you, or you can try to use smaller storage capacity and after you`ll get enough of RAM - expand it.

[Bhai]

When creating a new LSFS device of 8TB it says I need around 60GB RAM for caching (with no dedupe or autodefrag), and as I result of me only have 24GB spare it can only create a 6TB disk. With dedupe and defrag enabled it wants over 80GB RAM free!



______________________
Usman

[anton (staff)]

It's not a cache really these are in-memory hash tables. 5GB of RAM for 1TB of served capacity. Turn off dedupe to reduce requirements.

When creating a new LSFS device of 8TB it says I need around 60GB RAM for caching (with no dedupe or autodefrag), and as I result of me only have 24GB spare it can only create a 6TB disk. With dedupe and defrag enabled it wants over 80GB RAM free!