Compression and Hardware vs Software RAID

[Jheguy2]

I had asked earlier about upgrading my NAS about a month ago and recently bought a used Poweredge 2950 with 8GB of ECC memory and 4x 2TB WD Reds for a Raid-Z2 array. I am about to setup my initial configuration and was wondering if enabling compression and encryption on my volumes would be worth it in the long run. I would assume that compression would take a fair hit to read/write speeds and I would only save a few gigs by enabling it but I just wanted to make sure before I transfer 2TB of data over to my new NAS. Another question I had was involving using some drives as cache, the used server I bought included two 146gb 15k SAS drives and I was wondering if it was practical for me to use those in my NAS for cache or if it would bottleneck my array. Also, I wanted to make sure I should keep with my plan to software raid in FreeNAS rather than using my built in perc 5i raid card in my server. Thanks for the advice!

Edit: I also wanted to ask about backup services, because if I were to backup my old NAS to some sort of cloud service (I have "decent" internet so only about 48hr transfer time) I could upgrade my planned Raid-Z2 array to a 6 drive array as I had purchased a separate drive as a hotspare.

 

[enemy85]

Short answers:
1) DON'T use raid cards, FreeNas has its software raid;
2) at least since 9.2.1.5 version, compression is already set by default and works perfectly;
3)consider all the aspect of encryption before going for it...(much more hw resources involved, more complications, ecc.)
I'll suggest you to avoid it if you don't STRONGLY need it.

4) DON'T use raid cards!

 

[L]

The compression typically makes read/writes quicker as there is less to read/write. Modern cpus don't see the overhead people are used to seeing with compression and the disk is typically the slowest part of the system, so having less to write can improve performance.

I would only turn on encryption if necessary, like if I was designing a system for a bank, government or hospital.

Some of the value of software raid is that the underlying zfs in freenas has checksumming of the data blocks. This means it will if it finds a bad checksum, it will go get a good block(if there is redundancy, raid1 or z). Also, if you have to replace a drive, with raid cards they have to resync every block on the drive not matter if it has 1k of data on it or 1TB. It doesn't know what blocks hold data. With freenas and zfs, it does a process called resilver, where it only has to copy the data that is written.

For backup service, there are a number of zfs friendly cloud services. Code42 is a fairly reasonable priced service and crashplan is a plugin.

 

[HolyK]

Leave default (lz4) compression enabled. The amazing thing what it's doing is that it will NOT compress something which would be useless to compress. Things simplified ... it will compress only that kind of data with more than 12.5% compression ratio on ZFS pool. Anything bellow is stored as-is so the CPU horse power is not wasted.

And ... compression itself is really fast !!