Showing posts from 2014

Entropy analysis

This one is the most perfect example of entropy analysis I've seen done with ReclaiMe Pro to date

This one features three distinct frequencies. Think of entropy analyzer as of oscilloscope, giving you wavelength (inverse frequency) and phase. Block size is wavelength and block start offset is phase.

So there are three distinct wavelengths (block sizes)
16KB block of parity,4KB filesystem (NTFS) cluster1KB NTFS MFT entry size

NetGear ReadyNAS RN102

Been testing RN 102 from NetGear yesterday.

Performance is OK on large files, drops to slow death on smallish files.

Drive caddies are dreadful, especially on removal. When you try to remove the caddy, the caddy slips and the drive remains inside the unit. The retaining mechanism is probably broken by design. It also feels fragile. Earlier models with screws were way more solid, and way more reliable mechanically.

Storage Spaces again

Came across this, admittedly old, discussion about Storage Spaces

The fun starts at around post #4, with a real good piece of advice - your setting up a large drive system, read a LOT before committing your data to it for good.

Then the discussion touches the Drive Extender briefly. Storage Spaces is not Drive Extender. Indeed it is not. Storage Spaces is arguably more fragile, and undoubtedly Storage Spaces is more difficult to recover once failed. Way more difficult, I'd venture to say.

Then, around post #8, virtual machines come up. The common misconception is that recovery from storage system failures can be practiced with virtual machines. You'd better not. Virtual machines are good for modeling and training some normal operations of a storage system, but they are abysmal in reproducing storage behavior in failures.

In a virtual machine, all hardware is fail-stop. You cannot simulate bad bloc…

RAID rebuild time

Q: Once I have assembled RAID 5 with 5 disks of 1.5 TB in NAS QNAP, disks started to synchronize. 20 hours have passed but only 57% is done. Is this normal? It seems that array works OK (I have already copied data to it)

A: It is typical, especially if the array is also busy with copying data. For large arrays, first synchronization or a full rebuild (after drive replacement) often takes several days. It is advisable not to copy user data to the array until the first synchronization is complete because the array does not still provide redundancy and fault tolerance.

Flashing QNAP with disks removed

Q: I pulled the disks out of NAS QNAP to update firmware and then connected them back, but the NAS does not see nor does it initialize them. What should I do?
A: Try to pull the disks out once again, return to the old firmware, and then put the disks back. If it works, try to update firmware without removing the disks. One part of the operating system inside QNAP is stored in the built-in NAS memory while the second part is on disks themselves. Mismatch between these two parts leads to NAS refusal to work with disks.