Hi everyone:
The official FreeNAS docs (iSCSI page) "...a zvol and a file extent should have identical performance. In practice, a file extent outperforms in reads/writes but this is only noticeable at 10 GB Ethernet speeds or higher. For high performance, file extents are recommended at this time. "
My experience with this is the polarized opposite. Writing to a file extent I average write speeds of about 3.75MB/s. Writing to a device extent I average write speeds of about 88MB/s.
Usage: This is for a backup server. The goal is to use File extents so that I could expand my extents later as my backup storage needs grow. (My understanding is) File extents can be increased but device extents/zvol devices can either be created or destroyed - not grown.
UPDATE: I just read through to the bottom of the iSCSI page and saw zvol can be grown - just has to be done through the CLI (there doesn't appear to be a way to do it through the GUI. That's fine I guess - this seems to solve for the reason I was preferring File over Device extents)
Having said that, Is there a reason for the massive delta in speed between File and Device Extents? I ask only because the documentation (iSCSI page) says the opposite and I'd like to understand what I'm doing that is creating this massive difference.
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I will try to give as much information as possible. If anything else is needed to help me troubleshoot please let me know.
FreeNAS 9.2
Hardware: New Dell R520, 8x4TB Segate Constellation SAS 7200rpm drives, LSI 9211-8i controller. 32G RAM, dual processor Intel 2.2Ghz
Storage Server Configuration:
- Disk Raid: All drives in a Raidz2
Storage Volume
- StorageVolume: Compression: Inherit, aTime: Inherit, Quote and Reserved space: 0, DeDupe: Inherit
DataSet
-- StorageVolume\BackupDataSet: Compression Off; aTime: inherit; Quota for -this dataset, -this dataset and all children: 0; Reserved space for this dataset: 0; Reserved space for this dataset and all children: 1T; Dedupe: Inherit
-- zvol created under StorageVolume\BackupDataSet
Size: 1.5T; Compression: None; Sparse Volume: Unselected; Block Size 512
Extents
--- Extent Type: File; Path: StorageVolume\BackupDataset\FileExtent; Extent size: 1TB
--- Extent Type: Device; Path: StorageVolume\BackupDataset\DeviceExtent; Extent size: 1TB
iSCSI Config
Each iSCSI extent is presented through it's own identically configured Target to the testing server.
rw, logical block size: 512
The official FreeNAS docs (iSCSI page) "...a zvol and a file extent should have identical performance. In practice, a file extent outperforms in reads/writes but this is only noticeable at 10 GB Ethernet speeds or higher. For high performance, file extents are recommended at this time. "
My experience with this is the polarized opposite. Writing to a file extent I average write speeds of about 3.75MB/s. Writing to a device extent I average write speeds of about 88MB/s.
Usage: This is for a backup server. The goal is to use File extents so that I could expand my extents later as my backup storage needs grow. (My understanding is) File extents can be increased but device extents/zvol devices can either be created or destroyed - not grown.
UPDATE: I just read through to the bottom of the iSCSI page and saw zvol can be grown - just has to be done through the CLI (there doesn't appear to be a way to do it through the GUI. That's fine I guess - this seems to solve for the reason I was preferring File over Device extents)
Having said that, Is there a reason for the massive delta in speed between File and Device Extents? I ask only because the documentation (iSCSI page) says the opposite and I'd like to understand what I'm doing that is creating this massive difference.
---
I will try to give as much information as possible. If anything else is needed to help me troubleshoot please let me know.
FreeNAS 9.2
Hardware: New Dell R520, 8x4TB Segate Constellation SAS 7200rpm drives, LSI 9211-8i controller. 32G RAM, dual processor Intel 2.2Ghz
Storage Server Configuration:
- Disk Raid: All drives in a Raidz2
Storage Volume
- StorageVolume: Compression: Inherit, aTime: Inherit, Quote and Reserved space: 0, DeDupe: Inherit
DataSet
-- StorageVolume\BackupDataSet: Compression Off; aTime: inherit; Quota for -this dataset, -this dataset and all children: 0; Reserved space for this dataset: 0; Reserved space for this dataset and all children: 1T; Dedupe: Inherit
-- zvol created under StorageVolume\BackupDataSet
Size: 1.5T; Compression: None; Sparse Volume: Unselected; Block Size 512
Extents
--- Extent Type: File; Path: StorageVolume\BackupDataset\FileExtent; Extent size: 1TB
--- Extent Type: Device; Path: StorageVolume\BackupDataset\DeviceExtent; Extent size: 1TB
iSCSI Config
Each iSCSI extent is presented through it's own identically configured Target to the testing server.
rw, logical block size: 512