Home Server/RAID/ZFS

Tip: ZFS performs best when you spend time planning and researching your storage pool layout. Avoid jumping in and making mistakes with ZFS.

A long standing, reliable file system and software RAID solution that works on *BSD and Linux. Supports the standard RAID levels as well as RAID-Z.

ZFS needs at least 8GB RAM minimum. If it is starved for memory then your transfer speeds will decline. More RAM tends to increase the overall performance of your pool. 1GB per TB is a good rule if you are poor and 5GB per TB if you are rich.

ECC RAM

ECC RAM is a type of computer data storage that can detect and correct the most common kinds of internal data corruption. This type is recommended for obvious reasons and normally isn't much of a premium over regular RAM.

ECC isn't strictly required, but is an important component of reliable data storage. Here’s a quote from Matt Ahrens, one of the co-founders of the ZFS project at Sun Microsystems.

There's nothing special about ZFS that requires/encourages the use of ECC RAM more so than any other filesystem. If you use UFS, EXT, NTFS, btrfs, etc without ECC RAM, you are just as much at risk as if you used ZFS without ECC RAM. Actually, ZFS can mitigate this risk to some degree if you enable the unsupported ZFS_DEBUG_MODIFY flag. This will checksum the data while at rest in memory, and verify it before writing to disk, thus reducing the window of vulnerability from a memory error.
I would simply say: if you love your data, use ECC RAM. Additionally, use a filesystem that checksums your data, such as ZFS.

—Matt Ahrens, Ars OpenForum

There is endless debate over the requirement of ECC RAM for ZFS. The TL;DR of these innumerable arguments boils down to this:

ECC RAM is not strictly necessary for ZFS, but it is highly recommended. ECC RAM can detect and correct common kinds of data corruption, which complements ZFS's own data protection features. Without ECC RAM, certain types of data corruption may not be detected or corrected, potentially leading to data loss.

Additional ECC info:

• http://web.archive.org/web/20240220032547/https://cms-cdn.selinc.com/assets/Literature/Publications/White%20Papers/0004_ImportanceECCMemory_JH_20100716.pdf

RAID-Z

RAID-Z, a data/parity distribution scheme similar to RAID 5, but using dynamic stripe width: every block is its own RAID stripe, regardless of blocksize, resulting in every RAID-Z write being a full-stripe write. This, when combined with the copy-on-write transactional semantics of ZFS, eliminates the write hole error. RAID-Z can also detect and correct silent data corruption, offering "self-healing data". RAID-Z does not require any special hardware, such as NVRAM for reliability, or write buffering for performance.

—Wikipedia, Non-standard RAID levels

https://en.wikipedia.org/wiki/Non-standard_RAID_levels#RAID-Z https://en.wikipedia.org/wiki/ZFS#ZFS's_approach:_RAID-Z_and_mirroring https://jrs-s.net/2015/02/06/zfs-you-should-use-mirror-vdevs-not-raidz

RAID-Z has a number of benefits as well as drawbacks. Do your research and determine if RAID-Z is suitable for your use case.

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