雜錄與收藏

Recently we’ve been trouble shooting some weird SQL Server to file backup issues. They started failing on the clock at 06:00 AM. We checked the NICs, the switches, the drivers, the LUNs, HBAs, … but it was all well. We considered over stressed buffers as the root cause or spanning tree issues but the clock steadiness of it all was weird. We tried playing with some time out parameters but with little to no avail. Until the moment it hit me, the file deletions that clean up the old backups!We had UNMAP enabled recently on the SAN.
Take a look at the screenshot below an note the deletion times underlined in red. That’s with UNMAP enabled. Above is with UNMAP disabled. The Backup jobs failed waiting for the deletion process.

This is a no issues if your backup target is running something prior to Windows Server 2012. if not, UNMAP is disabled by default. I know about the potential performance impact of UNMAP when deleting or more larger files due to the space reclamation kicking in. This is described here Plan and Deploy Thin Provisioning under the heading “Consider space reclamation and potential performance impact”. But as I’m quite used to talking about many, many terabytes of data I kind of forget to think of 500 to 600GB of files as “big” . But it seemed to a suspect so we tested certain scenarios and bingo!

Windows 2012支援的SMB Multichannel結合一般網卡、RSS網卡、RDMA網卡所能達到的功能差異
 
 

 

 
 

Pooling of disks – 將實體磁碟丟到儲存池中，再產生virtual disk.

Continuous availability – 儲存池與磁碟可以由MS Failover cluster保護，所以若一部server故障，virtual disk與file share也能繼續提供服務。

Snapshots – 在儲存池上建立快照與clone。

Flexible resiliency options – 支援雙方鏡像，或三方鏡像，或是RAID 5或RAID0。在R2版本裡支援了可以將parity space用在cluster pool中，另外也支援dual parity選項。(enhanced in 2012 R2)

Enhanced Rebuilding – 重建failed disks效率提升. (enhanced in 2012 R2)

Storage Tiering – Windows Server 2012 R2支援使用不同的磁碟並自動搬移熱點資料(從SAS到SSD) (new in 2012 R2)

Write-Back Cache – 支援將資料先寫到SSD，之後再寫道較慢的硬碟。 (new in 2012 R2)

Data Deduplication – 重複刪除技術，已經在Windows Server 2012被支援，但是Windows Server 2012 R2再加強支援,讓CSV與VDI虛擬機能使用。 (enhanced in 2012 R2)

Management – Complete management solutions with Windows PowerShell, Failover Cluster, Server Manager or new in System Center 2012 R2 – Virtual Machine Manager. Now you can setup new Storage Servers, Storage Pools, Storage Spaces and File Shares directly from Virtual Machine Manager. (enhanced in 2012 R2)

ReFS – 在Windows Server 2012支援的功能，現在在R2也支援clustering，代表可以用在CSV上。